A2A Agent discovering and calling public MCP servers: results
wagerx · reddit · 2026-08-31
The author ran a structured test where an A2A agent (Wagie) discovered and validated MCP servers under strict rules.
- Constraints: Goals from an allowlist, no supplied endpoints, fresh MCP handshakes required, read-only tool calls only, no credentials or payments.
- Full Success: Discovered Microsoft Learn MCP, completed handshake, and called its documentation search tool.
- Handshake Success: Discovered "Professor Sausages Finance", completed handshake, and called finddata to list services, stopping before any payment flow.
- Secure Failure: EdgeDepth returned HTTP 401 on handshake. The agent correctly stopped without attempting to bypass auth.
- Lessons Learned: Discovery confidence ≠ endpoint health; exact identity matching is crucial to avoid substring attacks; MCP descriptions and tool results must be treated as untrusted input.
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