Expose an agent

Publish an existing AXL agent through A2A, MCP, or both by adding an interop table to its agent.toml.

Configure the public surface

key = "support"
name = "Partner support"
description = "Answers product and account questions."

[interop]
a2a = true
mcp_tool = true
public_description = "Investigates product and account questions for partners."
expose_skills = ["billing", "product-support"]

a2a publishes an Agent Card and JSON-RPC task endpoint.
mcp_tool publishes the agent as agent_support on AXL's MCP server.
public_description explains the agent to external clients. Keep secrets, internal routing details, and implementation notes out of it.
expose_skills limits the skills advertised through interoperability metadata. It does not grant new capabilities to the agent.

Restart AXL after changing agent configuration.

Configure the public URL

A2A cards contain absolute endpoint URLs, so the server needs its externally reachable base URL:

export PUBLIC_BASE_URL=https://axl.example.com

To publish one agent at the conventional well-known discovery path, set its key:

export A2A_WELL_KNOWN_AGENT=support

The agent remains available at its agent-specific path whether or not the well-known alias is configured.

Verify discovery

For A2A, fetch the Agent Card:

curl https://axl.example.com/a2a/support/agent-card.json

For MCP, connect a client to /mcp, list tools, and confirm agent_support appears. Then make a small read-only request before granting the integration production credentials.

Troubleshooting

The Agent Card has the wrong URL

Set PUBLIC_BASE_URL to the URL clients actually use, including the correct scheme and proxy hostname, then restart the server.

The MCP tool does not appear

Confirm mcp_tool = true, the agent key is valid, and the server was restarted after the configuration change.

A skill is missing from discovery

Add it to expose_skills only if it is intended for external use. The skill must also exist in the agent's normal configuration.

A2A partner quickstart - what your partners will do with this.
Connect an MCP client - the MCP half of the same configuration.
Authenticate callers - credentials for external clients.