startTool - CoreWeave Docs

startTool(opts: ToolInit): Tool

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

Throws if neither a Turn nor an LLM is active.

Parameters

ToolInit

required

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

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