MCP setup

How to serve MCP from Go and from the vlatte command. What an agent can do with it is in the MCP overview, and every tool is in Tools.

With admin.MCP(), the admin API serves its operations to AI agents too, over the Model Context Protocol: a tool per operation, named after it, such as add_mock, list_mocks and query_requests; the streams, the OpenAPI document and the pages have none. A tool's arguments carry what its route takes, the body under a key, such as {"mock": ...} for add_mock and {"query": ...} for query_requests, and its tool's schema names them. A tool answers what its route answers, or its problem document as the tool's error. An agent sees only the tools the server can do: a gRPC server has no mock_schema, and one without a journal no query_requests. verify_requests checks the requests as a Go test does, with the check under check.

api := admin.MustNew(admin.MCP())
m := mockhttp.MustNew(mockhttp.Setup().Admin(api).LogOutput(os.Stderr)) // over stdio, only MCP writes to stdout
m.MustStart()
fmt.Println(m.AdminURL() + "/mcp") // Streamable HTTP, for an agent that runs elsewhere
err := api.ServeMCP(ctx, os.Stdin, os.Stdout) // stdio, for an agent that starts the program, until stdin ends

POST /mcp keeps no sessions and answers in JSON. It needs the credentials the rest of the admin API needs, which an MCP client sends as Authorization: Bearer <token>: see Safety. MCP over stdio needs none: whoever holds the pipes started the program.

The vlatte command serves MCP at POST /mcp by default, and vlatte mcp serves it on stdin and stdout, for an agent that starts the command as its MCP server. vlatte mcp takes the server's flags, and writes its banner and logs to stderr. mcp: false (--mcp=false, VLATTE_MCP=false) turns MCP off. An agent's MCP settings start it as any command:

{"mcpServers": {"vlatte": {"command": "vlatte", "args": ["mcp", "--mock-files=mocks/*.yaml"]}}}