Tool annotations

Tool annotations: Hints on a tool such as readOnlyHint and destructiveHint that tell clients how risky a call is. Example: Claude's directory requires a title and readOnlyHint or destructiveHint on every tool. Next in the glossary is WebMCP: A draft browser API for pages to register JavaScript tools that an in-browser agent can call.

Definition

Hints on a tool such as readOnlyHint and destructiveHint that tell clients how risky a call is.

Example, with source

Claude's directory requires a title and readOnlyHint or destructiveHint on every tool. (claude.com, read 4 November 2026)

Where it appears on this site

• Getting listed in registries
• Tool descriptions and agent success

Neighbouring terms

• Tool: A function an MCP server offers for the model to call, with a name, description and input schema.
• WebMCP: A draft browser API for pages to register JavaScript tools that an in-browser agent can call.