Defined in: packages/ai/src/types.ts:1254
Emitted when a tool call starts.
@ag-ui/core provides: toolCallId, toolCallName, parentMessageId?
Field shapes are taken from AG-UI via Pick (not extends) so Zod .passthrough() index signatures do not pollute the StreamChunk discriminated union — required for KnownCustomEvent narrowing.
optional metadata?: Record<string, any>;Defined in: packages/ai/src/types.ts:1262
Provider-specific metadata to carry into the ToolCall.
optional toolName?: string;Defined in: packages/ai/src/types.ts:1260
Alias of toolCallName. Kept so existing stream readers still compile.
type: "TOOL_CALL_START";Defined in: packages/ai/src/types.ts:1258