Protocol
stdio
Learn how MCP stdio transport works, when local MCP servers use stdin/stdout, and how it compares with hosted HTTP endpoints.
Definition
stdio is an MCP transport where a client launches or connects to a local server process and exchanges JSON-RPC messages over standard input and standard output.
How Astrail Uses It
Astrail's hosted servers primarily use HTTP transport, while generated bundles and local development workflows may still reference stdio for client compatibility or local package scenarios.
Implementation Checklist
Keep protocol messages on stdout and logs on stderr.
Treat startup commands as trusted code that runs on the user's machine.
Use stdio for local integrations that need local files or tools.
Use hosted HTTP when the runtime should live behind server-side auth and monitoring.
FAQ
Does stdio require a public URL?
No. stdio usually runs locally, with the MCP client communicating directly with a child process or local executable.
Is stdio safer than HTTP?
It has different risks. stdio avoids a public network endpoint but can execute local code with the user's privileges, so package trust and install review matter.