startTool - Weights & Biases Documentation

startTool(opts): Tool

Start a Tool span. Parent resolution (matches the design’s “flat by default, hierarchical if you nest”):

If an LLM is active, the Tool nests under it.
Otherwise, the Tool is a sibling under the current Turn.

Throws if neither a Turn nor an LLM is active. Defined in: src/genai/api.ts:110

Parameters

opts

Returns

Tool

Examples

weave.startTool({
  name: 'get_weather',
  args: JSON.stringify({city: 'Tokyo'}),
  toolCallId: 'call_t1',
});

weave.startTool({
  name: 'get_weather',
  args: JSON.stringify({city: 'Tokyo'}),
  toolCallId: 'call_t1',
  startTime: new Date('2026-05-29T10:00:00.800Z'),
});