AGTP Composition Profiles

1.1. The Composition Problem

AGTP [AGTP] is a transfer protocol for AI agent traffic: the dedicated substrate on which that traffic runs, above TCP, QUIC, or HTTP/3 and below the agent frameworks. It is designed to compose with adjacent layers, each of which keeps its own role. Three categories of adjacent layer benefit from explicit composition profiles with AGTP:¶

Agent Group Messaging Protocols (AGMPs). Protocols such as MCP [MCP], A2A [A2A], ACP [ACP], and ANP [ANP] define agent-to- agent communication semantics: what agents say to each other, how tools are invoked, how tasks are delegated, how capabilities are advertised. These protocols are well-designed for what they address but share a common substrate limitation: they typically run over HTTP and inherit HTTP's constraints for agent traffic.¶

External identity providers. OAuth [RFC6749], OIDC, SPIFFE, enterprise IdPs, and similar services issue credentials that answer "on whose behalf is the agent acting." AGTP identity answers "which agent is making this call." The axes are orthogonal and require explicit composition rules so that they compose without conflict.¶

HTTP gateways. Many existing clients communicate over HTTP/REST and have no AGTP stack. Operators that want to expose AGTP-served agents to HTTP clients deploy translation gateways. The gateway is a deployment-time adoption ramp and no protocol of its own; the translation contract benefits from being specified explicitly so it is interoperable across implementations.¶

This document specifies the composition profile for each of these three categories. The profiles share a common architectural principle: AGTP headers take precedence over equivalent fields in the adjacent layer for all infrastructure-level routing, enforcement, and audit operations. Adjacent layers retain their own semantics and development paths.¶

1.2. The Limitation This Document Addresses

At the infrastructure layer, an A2A Task message carried over HTTP is indistinguishable from a human-initiated POST request. An MCP tool call carries no protocol-level signal of which agent sent it, under what authority, or within what resource budget. An OAuth bearer token in an HTTP request says "this principal is authenticated" but says nothing about which agent acted on that principal's behalf or with what authority scope. An HTTP gateway translating REST traffic into agent operations has no canonical mapping from HTTP verbs to agent semantics.¶

Governance, observability, and identity enforcement in such systems require application-layer instrumentation that is expensive, inconsistent, and invisible to routing infrastructure.¶

AGTP addresses this at the protocol layer. When messages from adjacent layers are carried over AGTP, every request carries the sending agent's verified identity and proof of key possession, its authority scope, its delegation lineage, and its resource budget in protocol headers, and resolves through the Agent-ID to an Identity Document that names the accountable owner. Infrastructure components -- load balancers, gateways, SEPs -- can route, filter, and enforce governance without parsing message payloads.¶

1.3. Relationship to AGTP Core

This document is a companion to [AGTP] and is normative for implementations that compose adjacent layers with AGTP. The core AGTP specification defines the protocol; this document defines how specific adjacent-layer concepts map to AGTP constructs. Implementations that use AGTP as the substrate for AGMP traffic, implementations that compose external identity providers with AGTP, and implementations that deploy HTTP gateways in front of AGTP agents MUST follow the mapping rules in this document.¶

1.4. Scope

This document covers three composition profile families:¶

1. AGMP composition profiles for MCP [MCP], A2A [A2A], and ACP [ACP] (Section 5).¶

2. External identity provider composition for OAuth, OIDC, and similar credential-issuing services (Section 9).¶

3. HTTP gateway composition for translation of HTTP traffic into AGTP method invocations (Section 10).¶

The document modifies no AGMP specification, no identity provider specification, and never HTTP. AGMPs retain their own schemas, semantics, and development paths. External identity providers retain their own credential formats and validation rules. HTTP retains its semantics. This document specifies only how adjacent-layer concepts relate to AGTP headers, methods, and operational contracts.¶

Additional composition surfaces specific to other AGTP companion specifications are addressed in those specifications:¶

• Payment provider composition is specified in [AGTP-COMMERCE].¶

• Credit bureau and trust provider composition is specified in [AGTP-TRUST].¶

• Certificate authority composition is specified in [AGTP-CERT].¶

• Institutional identity composition (LEI/vLEI) is specified in [AGTP-LEI].¶

This document covers only the three composition profile families named above. Composition surfaces in other documents compose with this document without being duplicated here. The strategic positioning, the substrate model, and the precedence rule are summarized in [AGTP]; this document is where the profiles and the wire examples live, including the AGMP wire-example appendix that earlier base revisions carried.¶

6.1. Overview

The Agent-to-Agent Protocol (A2A) [A2A] defines semantics for agent-to-agent task delegation, capability advertisement, artifact exchange, and provenance tracking. A2A runs over HTTP in its base specification. When running over AGTP, A2A messages are carried in AGTP request and response bodies, with A2A task, capability, and identity concepts mapped to AGTP headers.¶

6.2. A2A Concept Mapping

6.3. Mapping Rules

6.4. Wire Example: A2A Task over AGTP

The orchestrator acts under its own authority, so its DELEGATE carries no Delegation-Chain; the analyst's subsequent requests under the delegated scope carry one hop, <orchestrator Agent-ID>;<token>.¶

AGTP/1.0 DELEGATE /tasks
Agent-ID: agt-orchestrator
Authority-Scope: agents:delegate documents:query
Request-Signature: <JWS per AGTP>
Session-ID: sess-a1b2c3d4
Task-ID: task-0099
Budget-Limit: tokens=50000, ttl=300
Content-Schema: https://a2aprotocol.ai/schema/task/v1
Content-Type: application/agtp+json

{
  "method": "DELEGATE",
  "task_id": "task-0099",
  "parameters": {
    "target_agent_id": "agt-analyst",
    "authority_scope": "documents:query",
    "delegation_token": "<compact JWS, kid = agt-orchestrator>",
    "task": {
      "a2a_task_id": "a2a-task-7f3a",
      "message": {
        "role": "user",
        "parts": [{"type": "text",
          "text": "Summarize Q1 financial reports"}]
      },
      "artifacts": []
    }
  }
}

AGTP/1.0 200 OK
Server-ID: srv-acme-01
Agent-ID: agt-orchestrator
Task-ID: task-0099
Owner-ID: acme.tld
Attribution-Record: <JWS per AGTP-IDENTIFIERS>
Cost-Estimate: tokens=12450
Content-Type: application/agtp+json

{
  "status": 200,
  "task_id": "task-0099",
  "result": {
    "a2a_task_id": "a2a-task-7f3a",
    "status": "completed",
    "artifacts": [
      {
        "name": "Q1 Summary",
        "mimeType": "text/plain",
        "parts": [{"type": "text", "text": "..."}]
      }
    ]
  }
}

7.1. Overview

The Model Context Protocol (MCP) [MCP] defines structured communication between AI models and tools, resources, and context providers. MCP distinguishes between clients (AI models) and servers (tool/resource providers). When running over AGTP, MCP messages are carried in AGTP request and response bodies, with MCP session, context, and tool-call semantics mapped to AGTP constructs.¶

7.2. MCP Concept Mapping

7.3. Mapping Rules

7.4. Wire Example: MCP Tool Call over AGTP

AGTP/1.0 EXECUTE /tools
Agent-ID: agt-assistant
Authority-Scope: tools:web_search
Request-Signature: <JWS per AGTP>
Session-ID: sess-mcp-b2c3d4
Task-ID: task-0100
Budget-Limit: calls=1, ttl=60
Content-Schema: https://modelcontextprotocol.io/schema/tool-call/v1
Content-Type: application/agtp+json

{
  "method": "EXECUTE",
  "task_id": "task-0100",
  "parameters": {
    "action": "tools/call",
    "payload_type": "application/vnd.mcp+json",
    "idempotency_key": "01J9Z...",
    "payload": {
      "name": "web_search",
      "arguments": {
        "query": "IETF agent protocol drafts 2026"
      }
    }
  }
}

AGTP/1.0 200 OK
Server-ID: srv-acme-tools
Agent-ID: agt-assistant
Task-ID: task-0100
Attribution-Record: <JWS per AGTP-IDENTIFIERS>
Cost-Estimate: calls=1
Content-Type: application/agtp+json

{
  "status": 200,
  "task_id": "task-0100",
  "result": {
    "payload_type": "application/vnd.mcp+json",
    "content": [
      {
        "type": "text",
        "text": "draft-hood-independent-agtp-02 ..."
      }
    ]
  }
}

7.5. Wire Example: MCP Resource Fetch over AGTP

A resource read is read-only and maps onto QUERY, since no application-side action is performed. This is the example the base specification's appendix carried through v09.¶

AGTP/1.0 QUERY /resources
Agent-ID: agt-assistant
Authority-Scope: documents:query, knowledge:query
Request-Signature: <JWS per AGTP>
Session-ID: sess-mcp-b2c3d4
Task-ID: task-0102
Content-Type: application/agtp+json

{
  "method": "QUERY",
  "task_id": "task-0102",
  "parameters": {
    "intent": "fetch document corpus for Q1 financial analysis",
    "scope": ["documents:financial"],
    "modality": "mcp.resource",
    "mcp_resource_uri": "mcp://corpus/financial/q1-2026"
  }
}

7.6. Wire Example: MCP Sampling over AGTP

AGTP/1.0 EXECUTE /inference
Agent-ID: agt-assistant
Authority-Scope: inference:sample
Request-Signature: <JWS per AGTP>
Session-ID: sess-mcp-b2c3d4
Task-ID: task-0101
Budget-Limit: tokens=10000, ttl=120
Content-Type: application/agtp+json

{
  "method": "EXECUTE",
  "task_id": "task-0101",
  "parameters": {
    "action": "sampling/createMessage",
    "payload_type": "application/vnd.mcp+json",
    "payload": {
      "messages": [
        {
          "role": "user",
          "content": {
            "type": "text",
            "text": "Summarize these IETF drafts for me."
          }
        }
      ],
      "modelPreferences": {
        "hints": [{"name": "claude"}]
      },
      "maxTokens": 1000
    }
  }
}

8.1. Overview

The Agent Communication Protocol (ACP) [ACP] defines messaging semantics for agent-to-agent communication, including message routing, broadcast, and capability discovery. When running over AGTP, ACP messages are carried in AGTP request and response bodies.¶

8.2. ACP Concept Mapping

8.3. Mapping Rules

8.4. Wire Example: ACP Unicast Message over AGTP

AGTP/1.0 NOTIFY /messages
Agent-ID: agt-coordinator
Authority-Scope: agents:notify
Request-Signature: <JWS per AGTP>
Session-ID: sess-acp-c3d4e5
Task-ID: task-0201
Content-Type: application/agtp+json

{
  "method": "NOTIFY",
  "task_id": "task-0201",
  "parameters": {
    "recipient": "agt-worker-01",
    "content": {
      "acp_message_type": "task_assignment",
      "payload": {
        "task": "Process batch-2026-Q1",
        "deadline": "2026-04-01T00:00:00Z"
      }
    },
    "urgency": "normal",
    "delivery_guarantee": "at_least_once"
  }
}

9.1. The Two-Axis Model

AGTP identity and external IdP credentials answer different questions and MUST be treated as orthogonal axes:¶

• AGTP identity answers "which agent is making this call." Hash-anchored on the Agent Genesis ([AGTP]), presented via the Agent-ID header, proven per request by Request-Signature, optionally bound to a client certificate per [AGTP-CERT], scoped by Authority-Scope. The trust root is the Genesis-issuer registrar per [AGTP-TRUST].¶

• External IdP credentials answer "on whose behalf is the agent acting." A human principal, a service account, or a workload identity in an enterprise identity stack. The trust root is the IdP.¶

The axes compose. AGTP places no constraints on how external credentials are validated; servers MAY require external credentials on specific methods, MAY lift a named claim from the validated credential into the Attribution-Record, and MUST treat the failure modes of the two axes as independent.¶

9.2. Three Composition Patterns

Pattern 1: AGTP identity only. Agent-ID plus optional Agent Certificate plus Authority-Scope. No external IdP. Trust anchored in the Genesis-issuer registrar. Appropriate for closed agent ecosystems where the registrar is the trust root and no human-on-whose-behalf claim is required.¶

Pattern 2: AGTP identity plus external IdP credential. The request carries Agent-ID (wire-layer identity) and an Authorization header carrying an IdP-issued credential (application-layer principal). Both ride on the same request. AGTP Authority-Scope and external authorization scope (e.g., OAuth scopes per [RFC6749]) are independent: Authority-Scope is the agent's capacity to act, the IdP scope is the delegation from a principal authorizing the agent to do so on its behalf. A server's [policies.oauth] block (defined operationally outside this document) declares which methods require an external credential and which validator processes the credential. On validation success, the configured claim (typically sub) is lifted into the request context as the acting-principal identifier and stamped on the Attribution-Record as principal_id per [AGTP-IDENTIFIERS].¶

Pattern 3: OIDC-federated Genesis-issuer trust. The Genesis-issuer key itself is attested by an IdP. Trust anchors that would otherwise be a static trusted-registrars list are replaced by OIDC discovery: the verifier configures one or more OIDC anchors (discovery URL plus trusted issuer), fetches the JWKS at runtime, and confirms the issuer_public_key on the Agent Genesis matches one of the IdP's published keys. The Genesis schema is unchanged; the change is the resolution path the verifier uses to decide whether a recorded issuer key is trusted. See [AGTP-TRUST] for the trust-anchor schema.¶

9.3. Authorization Header

AGTP servers process the Authorization request header per HTTP semantics ([RFC9110]). The header value is opaque to AGTP itself; the configured validator interprets it. Common forms include:¶

• Bearer TOKEN: OAuth 2.0 / OIDC bearer tokens per [RFC6750].¶

• Other schemes (Basic, Digest, custom schemes): passed through to the configured validator unchanged.¶

Validation failures MUST return 401 Unauthorized with a response body carrying a structured reason from the vocabulary:¶

The 401 codes for external-credential failures are the same 401 code AGTP uses for other authentication failures; the reason field disambiguates.¶

9.4. Token Opacity and Attribution

AGTP MUST NOT stamp the raw Authorization header value or the raw token onto the Attribution-Record. The Attribution-Record is signed and may be replayed by chain walkers and audit consumers; embedding bearer tokens would create a credential-disclosure surface. Only the validated, lifted claim (the principal_id) appears on the Attribution-Record per [AGTP-IDENTIFIERS].¶

9.5. Backward Compatibility

The External IdP composition surface is opt-in. Servers with no [policies.oauth] configuration process requests identically to servers built without IdP composition awareness. Requests without an Authorization header on servers that require none are dispatched normally. This preserves Pattern 1 deployments byte-for-byte.¶

9.6. Wire Example: AGTP Request with OIDC Bearer Token

AGTP/1.0 EXECUTE /loans
Agent-ID: agt-loan-evaluator
Authority-Scope: loan:evaluate documents:read
Request-Signature: <JWS per AGTP>
Authorization: Bearer eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9...
Session-ID: sess-loan-eval-001
Task-ID: task-2026-0601
Content-Type: application/agtp+json

{
  "method": "EXECUTE",
  "task_id": "task-2026-0601",
  "parameters": {
    "payload_type": "application/vnd.bank.loan-eval+json",
    "action": "evaluate-application",
    "payload": {
      "application_id": "app-12345",
      "applicant_consent_ref": "consent-2026-001"
    }
  }
}

The bearer token in the Authorization header authorizes the loan-evaluator agent to act on behalf of a specific banking customer. The server's [policies.oauth] block requires Bearer tokens on the loan:evaluate scope, validates the token against the configured IdP, lifts the sub claim as principal_id, and stamps it on the Attribution-Record. The Identity Document that agt-loan-evaluator resolves to records the bank as owner (owner_id carrying an LEI-anchored institutional identity per [AGTP-LEI]); the bearer token identifies the customer. Owner and customer are independent axes.¶

10.1. Architectural Position

Operators that need to accept inbound HTTP/REST traffic on the same agent surface that serves AGTP MAY deploy an HTTP gateway sidecar alongside the AGTP daemon. The gateway is a parallel listener that accepts HTTP requests, translates them into AGTP method invocations, and dispatches them through the same response-finalization path as native AGTP traffic.¶

The gateway is no substitute for an AGTP binding. Two AGTP servers exchanging traffic with one another MUST NOT use the gateway as their hop; AGTP runs on its own bindings, and gateway-mediated AGTP-to-AGTP flows would lose the wire-level identity, attribution, and trust-posture guarantees AGTP defines. The gateway exists to translate non-AGTP clients into AGTP method invocations.¶

+--------------------+              +--------------------+
|  HTTP/REST Client  |  HTTP/1.1    |  HTTP Gateway      |
|  (non-AGTP-aware)  | -----------> |  (Sidecar)         |
+--------------------+              +--------------------+
                                              |
                                              | AGTP method
                                              | invocation
                                              v
                                    +--------------------+
                                    |  AGTP Daemon       |
                                    |  (port 4480)       |
                                    +--------------------+

10.2. Translation Rules

The gateway applies the following translation rules:¶

1. HTTP method to AGTP method. The HTTP method is run through the server's policies.methods.aliases map per [AGTP-METHODS]; the resolved canonical AGTP method is used for dispatch. The default alias seed (GET to FETCH, POST to CREATE, PUT to REPLACE, DELETE to REMOVE, PATCH to MODIFY) handles the five common verbs. The original HTTP method is preserved on the Attribution-Record as requested_method per [AGTP-IDENTIFIERS].¶

2. HTTP path to AGTP path. The path is forwarded verbatim, subject to the path grammar in [AGTP-METHODS].¶

3. HTTP headers to AGTP headers. The gateway MAY forward selected headers (e.g., Authorization mapped to AGTP authentication context per the External IdP composition profile in Section 9); the specific header forwarding policy is operator-defined.¶

4. Response. The AGTP response (status, headers, body) is translated into an HTTP response. The gateway MUST invoke the standard response-finalization path so the AGTP response carries a valid Attribution-Record; the resulting Audit-ID and Server-ID participate in the same per-agent chain as native AGTP responses.¶

10.3. Constraints

• The gateway **MUST strip the Allow-RCNS header from inbound HTTP requests before dispatch.** HTTP callers cannot opt into Runtime Contract Negotiation Substrate ([AGTP-RCNS]) through the gateway by design; RCNS is a substrate feature for AGTP-native callers whose identity, trust tier, and scope are bound at the AGTP layer. Operators that want to expose RCNS to HTTP callers MUST layer AGTP-native authentication on top of the gateway, in which case the gateway is no longer the right abstraction.¶

• The gateway is a translation surface and no binding. Two AGTP servers exchanging traffic with one another MUST NOT use the gateway as their hop; AGTP runs on its own bindings, and gateway-mediated AGTP-to-AGTP flows would lose the wire-level identity, attribution, and trust-posture guarantees this specification defines.¶

• The gateway **MUST NOT synthesize AGTP identity headers from HTTP request properties.** The Agent-ID forwarded to the AGTP daemon MUST be the gateway's own Canonical Agent-ID, signed with the gateway's own key in Request-Signature (the agent on whose behalf the gateway is calling into the AGTP layer); any identity inferred from the HTTP client is prohibited; the owner recorded on the gateway's Identity Document is therefore the gateway operator. HTTP clients that need authenticated agent identity at the AGTP layer MUST present credentials the gateway can validate and lift into a Pattern 2 External IdP composition.¶

10.4. Reference Deployment Pattern

The reference implementation pattern is an operational module distributed as mod_http_gateway or equivalent, listening on a separate port from the AGTP listener (default 127.0.0.1:8080 for the gateway, port 4480 for AGTP), so the two protocols never share a socket.¶

10.5. Wire Example: HTTP GET Translated to AGTP FETCH

GET /agents/library/books/2026-spring HTTP/1.1
Host: library.example.com
Authorization: Bearer eyJhbGciOiJSUzI1NiIs...
Accept: application/json

The gateway translates this to:¶

AGTP/1.0 FETCH /agents/library/books/2026-spring
Agent-ID: agt-http-bridge
Authority-Scope: catalog:read
Request-Signature: <JWS per AGTP, gateway key>
Authorization: Bearer eyJhbGciOiJSUzI1NiIs...
Session-ID: sess-http-bridge-9f3a
Task-ID: task-http-001
Content-Type: application/agtp+json

{
  "method": "FETCH",
  "task_id": "task-http-001",
  "parameters": {
    "path": "/agents/library/books/2026-spring",
    "format": "structured"
  }
}

The Agent-ID is the gateway's own agent identity; nothing is synthesized from the HTTP client. The bearer token from the HTTP request is forwarded and validated by the AGTP server's External IdP composition per Pattern 2. The original HTTP method (GET) is preserved on the Attribution-Record as requested_method for audit reconstruction.¶

12.1. Agent Discovery Across AGMPs

An agent registered with an AGTP governance platform is discoverable regardless of which AGMP it uses: it is found by search and discovered by Agent-ID per [AGTP-DISCOVERY] and [AGTP-PRESENCE]. The AGTP Agent Identity Document ([AGTP-IDDOC]) exposes the agent's supported methods and modalities; the AGTP DESCRIBE method exposes its capabilities. AGMP-specific capability formats (A2A Agent Cards, MCP capability lists) MAY be included as extensions to the AGTP Capability Document and are never required.¶

12.2. Session Continuity Across AGMPs

A single AGTP session MAY carry messages from multiple AGMPs within the same workflow. For example, an orchestrator agent might use A2A to delegate a task, then use MCP to invoke a tool within that task, all within a single AGTP session identified by the same Session-ID. AGTP session semantics ([AGTP-SESSION]) persist across AGMP message types within the session.¶

12.3. Identity Consistency Across Composition Families

An agent operating across multiple composition families MUST use the same canonical AGTP Agent-ID in all AGTP headers, regardless of which adjacent layer is composed. AGMP-layer identity fields (A2A agent.id, MCP client_id), external IdP claims, and HTTP-client identifiers MAY differ from the canonical AGTP Agent-ID for backward compatibility with non-AGTP deployments, but the AGTP Agent-ID is authoritative for all governance and audit purposes.¶

12.4. IdP and Gateway Combined

An HTTP request with a Bearer token arriving at an HTTP gateway composes both the External IdP profile and the HTTP Gateway profile:¶

1. The gateway translates the HTTP request to an AGTP method invocation per Section 10, forwarding the Authorization header.¶

2. The AGTP server validates the bearer token per the External IdP composition Pattern 2 in Section 9, lifting the configured claim as principal_id.¶

3. The Attribution-Record carries both the gateway's Agent-ID (which agent invoked the method) and the lifted principal_id (on whose behalf the call was made).¶

The gateway is the agent at the AGTP layer; the bearer token's subject is the principal. Both fit the existing two-axis model.¶

13.1. AGMP Payload Injection

Threat: A malicious actor embeds forged identity or scope fields in an AGMP message payload, attempting to override or supplement the AGTP header values with elevated permissions.¶

Mitigation: Infrastructure components MUST NOT parse AGMP payloads for identity or scope information. The precedence rule in Section 4 is absolute: AGTP headers govern all infrastructure decisions. Application code SHOULD validate that AGMP payload identity fields are consistent with the AGTP headers and MUST reject requests where they conflict in ways that suggest an escalation attempt.¶

13.2. Cross-AGMP Delegation Elevation

Threat: An agent uses AGMP composition to cross protocol boundaries in a way that circumvents AGTP scope enforcement. For example, receiving a task via A2A with a delegated scope, then re-delegating it via MCP with an elevated scope.¶

Mitigation: the delegation rules of [AGTP] apply unchanged across AGMP boundaries. Each re-delegation is a new AGTP DELEGATE invocation, minting a new hop whose scope is a strict subset of the delegating agent's effective scope, and every request under the delegated authority carries the full Delegation Sequence, which the receiving server verifies hop by hop. An elevation attempted through an AGMP payload fails at the first conformant verifier, because the payload carries no authority (Section 4).¶

13.3. Payload Schema Validation

Implementers SHOULD use the Content-Schema header (Section 11) to declare the schema of the AGMP payload. Recipients SHOULD validate the payload against the declared schema before processing. This mitigates injection attacks that rely on schema ambiguity at the AGMP layer.¶

13.4. Bearer Token Leakage via Attribution-Record

Threat: An implementation incorrectly stamps the raw Authorization header value or the raw bearer token onto the Attribution-Record. Since Attribution-Records are signed and may be replayed by chain walkers and audit consumers, this would create a credential-disclosure surface.¶

Mitigation: AGTP MUST NOT stamp the raw Authorization header value or the raw token onto the Attribution-Record. Only the validated, lifted claim (the principal_id) appears on the Attribution-Record per [AGTP-IDENTIFIERS]. Implementations MUST verify this constraint in their attribution-record builder before release.¶

13.5. External IdP Validator Confusion

Threat: A server with multiple configured IdP validators dispatches a credential to the wrong validator, causing a credential issued by one IdP to be interpreted as if issued by another. An attacker could exploit this to present a credential to a validator that accepts it when the intended validator would have rejected it.¶

Mitigation: Servers MUST route credentials to the correct validator based on policy-defined matching rules (token issuer, audience claim, header marker). Servers MUST NOT dispatch a credential to multiple validators in parallel and accept any success; this creates the confusion surface described above.¶

13.6. HTTP Gateway Identity Synthesis

Threat: An HTTP gateway implementation synthesizes AGTP identity headers from HTTP request properties (client IP, user-agent string, hostname), creating a forgeable identity surface.¶

Mitigation: The gateway MUST NOT synthesize Agent-ID from HTTP request properties per the constraints in Section 10, and cannot forge Request-Signature for an identity whose key it lacks. The Agent-ID forwarded to the AGTP daemon MUST identify the gateway's own agent identity. HTTP clients that need authenticated agent identity at the AGTP layer MUST present credentials the gateway can validate and lift into a Pattern 2 External IdP composition.¶

13.7. HTTP Gateway RCNS Bypass

Threat: An HTTP client attempts to opt into Runtime Contract Negotiation Substrate (RCNS) through the gateway by sending an Allow-RCNS header, gaining access to a substrate feature that is designed for AGTP-native callers with bound identity, trust tier, and scope.¶

Mitigation: The gateway MUST strip the Allow-RCNS header from inbound HTTP requests before dispatch per Section 10. Operators that want to expose RCNS to HTTP-originating callers MUST layer AGTP-native authentication on top of the gateway, in which case the gateway is no longer the right abstraction.¶

15.1. Substantive Changes

1. Owner identity is a document field. Owner-ID is removed from the precedence header list, the A2A mapping, the mapping rules, and all wire examples; the owner is read from the Agent Identity Document the Agent-ID resolves to ([AGTP-IDDOC]). The response-side Owner-ID header of [AGTP] is unaffected.¶

2. Delegation restated against base v10. The A2A provenance rule now maps to the Delegation Sequence (pre-authorization) and prior_actions (attribution), with the hop format, token signer, and verification rules by reference to [AGTP]; the independent MUSTs of v01 are withdrawn. The DELEGATE example no longer carries Delegation-Chain on an undelegated invocation, and delegation_token is the parent's signature, where v01 had a governance-platform token.¶

3. MCP tool calls and sampling move from QUERY to EXECUTE. QUERY is safe and early-data eligible; a tool call may have side effects and sampling consumes budget. EXECUTE with payload_type: application/vnd.mcp+json is the carrier [AGTP] names. Resource reads and prompts stay on QUERY. The MCP resource fetch example from the base appendix is added.¶

4. Request-Signature shown on every example; Agent-ID values shown as canonical identifiers; request lines carry a path; Server-Agent-ID replaced by Server-ID and the Attribution-Record signer.¶

5. Content-Schema specified (Section 11) as the reserved header's home, with the 422 reason schema-mismatch.¶

6. Agent Card distinguished from Agent Identity Document: a self-asserted description versus an issuer-signed credential.¶

7. AGMP wire-example appendix from base v09 absorbed; the base document now summarizes and points here.¶

8. Title shortened to "AGTP Composition Profiles"; the three families remain the first sentence of the abstract.¶

9. References: base to -10; AGTP-API split into AGTP-METHODS and AGTP-RCNS; AGTP-IDENTIFIERS -03, AGTP-LOG -03, AGTP-DISCOVERY -02, AGTP-PRESENCE -01, AGTP-LEI -01, AGTP-COMMERCE -01; AGTP-IDDOC and AGTP-SESSION added. Transfer-protocol wording in place of transport. House style pass.¶

15.2. Wire Format Compatibility

Removing Owner-ID from requests and moving MCP tool calls to EXECUTE are breaking for v01 implementations of those two profiles; both track changes already made in base AGTP v10, so a v01 implementation updated to base v10 needs the same changes. The A2A header shape is otherwise unchanged. Content-Schema is additive.¶

16.1. Substantive Changes

1. Title expanded to "AGTP Composition Profiles: Agent Group Messaging Protocols, External Identity Providers, and HTTP Gateways" reflecting the broader scope.¶

2. External Identity Provider composition profile added as Section 9. Three composition patterns (AGTP-only, AGTP+IdP, OIDC-federated Genesis trust). Authorization header semantics. Token opacity rule. 401 reason vocabulary (oauth-required, oauth-invalid). Backward compatibility guidance. Wire example showing OIDC bearer token composition.¶

3. HTTP Gateway composition profile added as Section 10. Architectural position. Translation rules (HTTP method to AGTP method via alias map; HTTP path verbatim; header forwarding policy; response finalization). Constraints (Allow-RCNS header stripping; transport-vs-translation distinction; no identity synthesis from HTTP properties). Reference deployment pattern. Wire example showing HTTP GET translated to AGTP FETCH.¶

4. Cross-AGMP Interoperability renamed and broadened to Cross-Composition Interoperability. New subsection covering the combined IdP-plus-Gateway case.¶

5. Identifier rename applied throughout. The Principal-ID wire header is renamed to Owner-ID in all AGMP mapping tables, mapping rules, and wire examples, tracking the locked AGTP taxonomy from [AGTP-IDENTIFIERS].¶

6. Security Considerations expanded to cover the new profile families. Four new subsections: Bearer Token Leakage via Attribution-Record; External IdP Validator Confusion; HTTP Gateway Identity Synthesis; HTTP Gateway RCNS Bypass.¶

7. Normative reference to [AGTP] updated to v08 (was v02 in v00).¶

8. Informative references added to AGTP-API (since split into [AGTP-METHODS] and [AGTP-RCNS]), [AGTP-IDENTIFIERS], [AGTP-TRUST], [AGTP-LOG], [AGTP-PRESENCE], [AGTP-LEI], [AGTP-COMMERCE], and [AGTP-DISCOVERY], reflecting the broader AGTP draft family that has emerged since v00 of this document.¶

9. Normative reference to [RFC9110] added to support the Authorization header semantics in the External IdP composition profile. Informative references to [RFC6749] (OAuth 2.0) and [RFC6750] (Bearer tokens) added.¶

10. Method floor references updated. Where v00 referenced the 12-method or 16-method floor, v01 references the current 18-method floor per [AGTP].¶

16.2. Composition Profile Boundary Clarifications

This document covers three composition profile families. Other composition surfaces specific to AGTP companion specifications are addressed in those specifications and only referenced here:¶

• Payment provider composition is specified in [AGTP-COMMERCE].¶

• Credit bureau and trust provider composition is specified in [AGTP-TRUST].¶

• Certificate authority composition is specified in [AGTP-CERT].¶

• Institutional identity composition (LEI/vLEI) is specified in [AGTP-LEI].¶

16.3. Wire Format Compatibility

The v01 changes are additive (new profile families, expanded security considerations, broader scope) and identifier-alignment (Principal-ID to Owner-ID rename). No AGMP composition wire format changes are introduced beyond the identifier rename that tracks the broader AGTP taxonomy update. Implementations conforming to v00 require the Owner-ID rename to interoperate with v01 implementations and AGTP v08 servers.¶

17.1. Normative References

[AGTP]

Hood, C., "Agent Transfer Protocol (AGTP)", Work in Progress, Internet-Draft, draft-hood-independent-agtp-10, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-independent-agtp-10>.

[RFC2119]

Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/rfc/rfc2119>.

[RFC8174]

Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.

[RFC9110]

Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, Ed., "HTTP Semantics", STD 97, RFC 9110, DOI 10.17487/RFC9110, June 2022, <https://www.rfc-editor.org/rfc/rfc9110>.

17.2. Informative References

[A2A]

Linux Foundation, "Agent-to-Agent Protocol Specification", 2025, <https://a2aprotocol.ai>.

[ACP]

IBM Research, "Agent Communication Protocol", 2025.

[AGTP-CERT]

Hood, C., "AGTP Agent Certificate Extension", Work in Progress, Internet-Draft, draft-hood-agtp-agent-cert-04, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-agtp-agent-cert-04>.

[AGTP-COMMERCE]

Hood, C., "AGTP-Commerce: Open Commerce Specification for Agent-to-Agent Transactions", Work in Progress, Internet-Draft, draft-hood-agtp-commerce-01, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-agtp-commerce-01>.

[AGTP-DISCOVERY]

Hood, C., "AGTP Discovery and Naming", Work in Progress, Internet-Draft, draft-hood-agtp-discovery-02, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-agtp-discovery-02>.

[AGTP-IDDOC]

Hood, C., "AGTP Agent Identity Document", Work in Progress, Internet-Draft, draft-hood-agtp-identity-document-00, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-agtp-identity-document-00>.

[AGTP-IDENTIFIERS]

Hood, C., "AGTP Identifier Chain", Work in Progress, Internet-Draft, draft-hood-agtp-identifiers-03, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-agtp-identifiers-03>.

[AGTP-LEI]

Hood, C., "AGTP Binding to the Legal Entity Identifier (LEI and vLEI)", Work in Progress, Internet-Draft, draft-hood-agtp-lei-01, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-agtp-lei-01>.

[AGTP-LOG]

Hood, C., "AGTP Transparency Log", Work in Progress, Internet-Draft, draft-hood-agtp-log-03, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-agtp-log-03>.

[AGTP-METHODS]

Hood, C., "AGTP Methods (AGTP Verbs)", Work in Progress, Internet-Draft, draft-hood-agtp-methods-00, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-agtp-methods-00>.

[AGTP-PRESENCE]

Hood, C., "AGTP Presence: Ambient Discovery and Visibility for Agents", Work in Progress, Internet-Draft, draft-hood-agtp-presence-01, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-agtp-presence-01>.

[AGTP-RCNS]

Hood, C., "AGTP Runtime Contract Negotiation Substrate", Work in Progress, Internet-Draft, draft-hood-agtp-rcns-00, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-agtp-rcns-00>.

[AGTP-SESSION]

Hood, C., "AGTP Session Protocol", Work in Progress, Internet-Draft, draft-hood-agtp-session-01, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-agtp-session-01>.

[AGTP-TRUST]

Hood, C., "AGTP Trust and Verification Specification", Work in Progress, Internet-Draft, draft-hood-agtp-trust-03, 2026, <https://datatracker.ietf.org/doc/html/draft-hood-agtp-trust-03>.

[ANP]

"Agent Network Protocol", 2025.

[MCP]

Anthropic, "Model Context Protocol", 2024, <https://modelcontextprotocol.io>.

[RFC6749]

Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", RFC 6749, DOI 10.17487/RFC6749, October 2012, <https://www.rfc-editor.org/rfc/rfc6749>.

[RFC6750]

Jones, M. and D. Hardt, "The OAuth 2.0 Authorization Framework: Bearer Token Usage", RFC 6750, DOI 10.17487/RFC6750, October 2012, <https://www.rfc-editor.org/rfc/rfc6750>.