MCP stdio Transport

In addition to the HTTP JSON-RPC transport, rustapi mcp generate supports --stdio.

stdio is the transport used by many local AI clients (Claude Desktop, some Cursor setups, custom agents) that spawn the MCP server as a child process and communicate over stdin/stdout.

Usage

rustapi mcp generate \
  --spec ./openapi.json \
  --target http://localhost:8000 \
  --stdio

When --stdio is passed, the command does not bind a TCP port. Instead it enters a loop:

• Reads JSON-RPC lines from stdin
• Dispatches initialize, tools/list, tools/call
• Writes JSON-RPC responses to stdout

Why stdio?

• No network port to manage or firewall.
• Simple process model for desktop apps.
• Works well with local-only tools.

Current Limitations (MVP)

• Only basic JSON-RPC over line-delimited messages (no SSE framing yet).
• No built-in auth/token for stdio (rely on OS process isolation + tool-level filters).
• Logging goes to stderr.

Connecting Clients

Most clients that support “local MCP server” or “command” transport can use:

{
  "command": "rustapi",
  "args": ["mcp", "generate", "--spec", "/path/to/openapi.json", "--target", "http://127.0.0.1:8000", "--stdio"]
}

See your client’s documentation for exact config format.

Related Pages

• Main MCP: MCP Integration
• In-process: MCP In-Process Invocation
• CLI generator: OpenAPI to MCP CLI