WebMCP Tool Annotations

Before writing code

Fetch live docs:

1. Fetch https://webmachinelearning.github.io/webmcp/ for the annotations specification
2. Web-search webmcp tool annotations readOnlyHint destructiveHint idempotentHint for annotation field details
3. Web-search site:developer.chrome.com webmcp annotations permissions for how Chrome uses annotations
4. Web-search site:github.com mcp-b annotations for polyfill support for annotations

Conceptual Architecture

What Annotations Are

Tool annotations are optional metadata attached to a tool definition that inform the browser and agent about the tool's behavior and safety characteristics. The browser uses annotations to decide whether to prompt the user for confirmation before allowing agent invocation.

Available Annotations