MCP Receipt Governed

MCP tool-call receipt signing integration for Agent Governance Toolkit.

Every MCP tool invocation optionally produces a signed governance receipt linking the Cedar policy decision to the tool call, providing a cryptographically verifiable audit trail for agent operations.

Quick Start

from mcp_receipt_governed import McpReceiptAdapter

adapter = McpReceiptAdapter(
    cedar_policy="""
        permit(principal, action == Action::"ReadData", resource);
        forbid(principal, action == Action::"DeleteFile", resource);
    """,
    cedar_policy_id="policy:mcp-tools:v1",
    signing_key_hex="a" * 64,  # Replace with real Ed25519 seed
)

# Govern a tool call — produces a signed receipt
receipt = adapter.govern_tool_call(
    agent_did="did:mesh:agent-1",
    tool_name="ReadData",
    tool_args={"path": "/data/report.csv"},
)

print(f"Decision: {receipt.cedar_decision}")
print(f"Receipt ID: {receipt.receipt_id}")
print(f"Signed: {receipt.signature is not None}")

Features

• Cedar policy binding: Receipt payload includes the Cedar policy ID and allow/deny decision
• Ed25519 signatures: Non-repudiable receipt signing with HMAC-SHA256 fallback
• Canonical JSON hashing: JCS-style deterministic serialization for verifiable receipts
• Receipt store: In-memory audit trail with filtering by agent, tool, or decision
• Zero required dependencies: Works with stdlib only; Ed25519 signing available via pip install agentmesh-mcp-receipts[crypto]

Installation

# From the repository root
pip install -e agent-governance-python/agentmesh-integrations/mcp-receipt-governed

# With Ed25519 signing support
pip install -e "agent-governance-python/agentmesh-integrations/mcp-receipt-governed[crypto]"

Testing

cd agent-governance-python/agentmesh-integrations/mcp-receipt-governed
pip install -e ".[dev]"
pytest tests/ -v

Architecture

MCP Tool Call
     │
     ▼
┌────────────────────┐
│  McpReceiptAdapter │
│  ┌──────────────┐  │
│  │ Cedar Policy │──┼──▶ allow / deny
│  │  Evaluator   │  │
│  └──────────────┘  │
│  ┌──────────────┐  │
│  │  Receipt     │──┼──▶ GovernanceReceipt
│  │  Generator   │  │    (tool, agent, policy, decision)
│  └──────────────┘  │
│  ┌──────────────┐  │
│  │  Ed25519     │──┼──▶ Signed receipt
│  │  Signer      │  │
│  └──────────────┘  │
│  ┌──────────────┐  │
│  │ ReceiptStore │──┼──▶ Audit trail
│  └──────────────┘  │
└────────────────────┘

License

MIT — see LICENSE.