Protocol
tools/list
Learn how tools/list lets MCP clients discover available tools, schemas, descriptions, and safe invocation metadata.
Definition
tools/list is the MCP method clients use to discover which tools a server exposes. A useful tools/list response gives the model enough names, descriptions, schemas, and metadata to decide which operation to request.
How Astrail Uses It
Astrail uses tools/list as the public catalog for generated servers. Private tools are filtered at the hosted MCP boundary so unauthenticated or unauthorized clients do not see operations they cannot call.
Implementation Checklist
Return only tools the current caller is allowed to know about.
Keep tool names and descriptions stable across generations when possible.
Include input schemas that match runtime validation.
For large APIs, consider a small tools/list surface plus search_docs and execute.
FAQ
Does tools/list execute anything?
No. tools/list is discovery. Execution happens through tools/call after the client selects a specific tool and sends arguments.
Can tools/list be different for different users?
Yes. A hosted MCP endpoint can filter tools based on auth, tenancy, plan limits, or server visibility policy.