The Secure Task-bound Agent Message Proof (STAMP) protocol provides a cryptographically verifiable delegation and proof framework for AI- driven multi-agent systems. STAMP introduces task-bound access tokens and message-level proofs for agentic environments, binding tokens to specific user intents, tasks, and agent identities. STAMP tokens ensure that delegation, execution, and agent-to-agent communication comply with least-privilege and zero-trust security principles. STAMP interoperates with OAuth 2.0, GNAP, and modern proof-of- possession (PoP) techniques, providing stronger security for dynamic, non-deterministic workflows involving autonomous agents.