stdio transport

stdio transport: The MCP binding where a client launches the server as a subprocess and exchanges newline-delimited JSON-RPC over standard streams. Example: Apify's local server runs with npx @apify/actors-mcp-server over stdio. Next in the glossary is Step-up authorization: Requesting a wider scope set after a 403 insufficient_scope challenge, keeping previously granted scopes.

Definition

The MCP binding where a client launches the server as a subprocess and exchanges newline-delimited JSON-RPC over standard streams.

Example, with source

Apify's local server runs with npx @apify/actors-mcp-server over stdio. (docs.apify.com, read 4 November 2026)

Where it appears on this site

• MCP
• Building a remote MCP server

Neighbouring terms

• Stateless MCP: The 2026-07-28 model with no initialize handshake and no Mcp-Session-Id; each request carries version and capabilities in _meta.
• Step-up authorization: Requesting a wider scope set after a 403 insufficient_scope challenge, keeping previously granted scopes.
• Streamable HTTP: The MCP HTTP binding where each message is a POST to one endpoint and replies come as JSON or a request-scoped SSE stream.