keycard/keycard
Add Keycard auth to MCP servers, REST APIs, and A2A agents
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- name:
- keycard-a2a-agent
- description:
- Building an A2A (Agent-to-Agent) protocol server governed by Keycard, creating a Keycard-protected AI agent service, or implementing agent-to-agent delegation chains
Build a Keycard-Governed A2A Agent
Install
Python: pip install keycardai-a2a uvicorn
TypeScript: npm install @keycardai/a2a @a2a-js/sdk express
Canonical examples — read these before writing any code
- Python: packages/a2a/examples/keycard_protected_server/main.py
- TypeScript:
@keycardai/a2aREADME
Keycard Console setup
- Zone ID from Zone Settings
- Applications → Create Application (A2A agents are Applications, not Resources — they have an identity, not just an audience)
- Generate Client ID + Client Secret — the agent authenticates to Keycard with these to verify inbound tokens and perform delegation
keycard.toml (for keycard run sessions)
[zone]
id = "<your-zone-id>"Accessing the caller's identity in your executor
The verified user is available via context.call_context.state["access_token"] (Python) or getKeycardAuth(requestContext).token (TypeScript). Use this as the subject_token in an RFC 8693 token exchange when calling downstream services to maintain the delegation chain.
Common errors
| Error | Cause | Fix |
|---|---|---|
| 401 on all A2A requests | Expected — require_authentication=True on the JSONRPC mount | Callers must present a Keycard bearer token |
access_token missing from executor context | KeycardServerCallContextBuilder not wired | Pass context_builder=KeycardServerCallContextBuilder() to create_jsonrpc_routes (Python) or use createKeycardRequestHandler (TypeScript) |
| Agent card empty or missing capabilities | AgentServiceConfig missing description or capabilities | Set both fields in the config object |
| Delegation chain not propagating | Caller token not forwarded as subject_token | Read context.call_context.state["access_token"] and pass it as subject_token in downstream token exchange |
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- keycard
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