CustomTool

Inline custom tool — registered with the LLM under the given name + schema and dispatched locally to CustomTool.handler when the model emits a tool_use for it.

Local runtime only (SDK v1.0). Cloud agents reject tools (handlers cannot cross the wire — use MCP servers or subagents for cloud tool surfaces).

Handlers MUST be re-passed on Agent.resume() because closures cannot be persisted. The tool catalog (name + description + schema) is NOT serialized.

Signature

interface CustomTool { /* ... */ }

Kind

interface

Source

packages/sdk/src/types/agent.ts:271