Open source · MIT

MCP client compatibility fixture

A deterministic local server for comparing MCP client behavior against the same Streamable HTTP endpoint. It exposes two read-only tools, rejects invalid bearer credentials, and has no filesystem, database, or external network capability.

This is a test fixture, not a production MCP server. Use a throwaway token and keep the listener on 127.0.0.1.

Source files

handler.ts Deterministic Streamable HTTP handler server.ts Local Deno server bound to 127.0.0.1 handler_test.ts Ten transport and contract tests README.md Run and verification instructions

Verified scope

Deno type checking and ten handler tests pass. A raw local HTTP sequence also verified authentication, initialization, tool discovery, and one successful call. No claim is made about a client until that client is tested separately.

MIT license MCP testing article