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Connect a tool without lending it authority

Distinguish a tool's interface from permission to access its data.

Read the concept. Explore two decisions. Leave with a test you would run next.

The working model

Understand the boundary.

Model Context Protocol (MCP) describes how a client discovers and calls tools. A tool schema explains the interface; it does not prove that a particular caller may use a particular record. Validate inputs and enforce authorization where the operation executes.

Request
Typed arguments describe a call
Check
Authenticated scope limits access
Return
Only permitted data leaves the tool

A worked example

A fictional search_records tool accepts a record ID. The server resolves the caller's allowed workspace from its authenticated session, then checks the record belongs to that workspace. A workspace ID in model-generated arguments is not a trusted identity source.

MCP: tools and security considerations

Primary reading checked 2026-10-10. Provider learning stays with its issuer.

Practice deskDecision 1 of 2

Make a decision

A valid tool call includes workspace_id=other-workspace. The caller's authenticated session belongs to a different workspace.

Where should the tool get its authority?

Choose one response before comparing the reasoning.Accept the workspace ID because the call matches the schema.Resolve allowed scope from the authenticated session and refuse access outside it.Read the other workspace, then hide its name in the response.

Another concept

Validate meaning after validating shape

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