ToolAnnotations

Behavioral hints for a tool (MCP annotations, spec 2025-06-18 / 2025-11-25).

Hosts use these to decide confirmation friction and whether a tool reaches the open world. Per the spec, the conservative absence default treats a tool as readOnlyHint: false, destructiveHint: true, openWorldHint: true — so the SDK auto-derives a safer readOnlyHint default (see ToolDefinition). Clients MUST treat annotations as untrusted unless the server is trusted.

Properties

Property	Type	Description
destructiveHint?	boolean	True if the tool may perform destructive updates (meaningful only when not read-only).
idempotentHint?	boolean	True if repeated calls with the same arguments have no additional effect.
openWorldHint?	boolean	True if the tool interacts with external entities (the open world).
readOnlyHint?	boolean	True if the tool does not modify its environment.