BeforeToolCallEvent

Event triggered just before a tool is executed. Fired after tool lookup but before execution begins. Hook callbacks can set cancel to prevent the tool from executing.

Extends

HookableEvent

Constructors

Constructor

new BeforeToolCallEvent(data): BeforeToolCallEvent;

Defined in: src/hooks/events.ts:229

Parameters

Parameter	Type
`data`	{ `agent`: `LocalAgent`; `toolUse`: { `name`: `string`; `toolUseId`: `string`; `input`: `JSONValue`; }; `tool`: `Tool`; `invocationState`: `InvocationState`; }
`data.agent`	`LocalAgent`
`data.toolUse`	{ `name`: `string`; `toolUseId`: `string`; `input`: `JSONValue`; }
`data.toolUse.name`	`string`
`data.toolUse.toolUseId`	`string`
`data.toolUse.input`	`JSONValue`
`data.tool`	`Tool`
`data.invocationState`	`InvocationState`

Returns

BeforeToolCallEvent

Overrides

HookableEvent.constructor

Properties

type

readonly type: "beforeToolCallEvent";

Defined in: src/hooks/events.ts:212

agent

readonly agent: LocalAgent;

Defined in: src/hooks/events.ts:213

toolUse

readonly toolUse: {
  name: string;
  toolUseId: string;
  input: JSONValue;
};

Defined in: src/hooks/events.ts:214

name

name: string;

toolUseId

toolUseId: string;

input

input: JSONValue;

tool

readonly tool: Tool;

Defined in: src/hooks/events.ts:219

invocationState

readonly invocationState: InvocationState;

Defined in: src/hooks/events.ts:220

cancel

cancel: string | boolean = false;

Defined in: src/hooks/events.ts:227

Set by hook callbacks to cancel this tool call. When set to true, a default cancel message is used. When set to a string, that string is used as the tool result error message.

Methods

toJSON()

toJSON(): Pick<BeforeToolCallEvent, "type" | "toolUse">;

Defined in: src/hooks/events.ts:246

Serializes for wire transport, excluding the agent reference, tool instance, invocationState, and mutable cancel flag. Called automatically by JSON.stringify().

Returns

Pick<BeforeToolCallEvent, "type" | "toolUse">