Unverified50% confidenceFactExact time
When the model decides to use a tool, the stop_reason in the Claude API response changes to tool_use, and a tool_use block containing the tool ID, name, and input parameters appears.
1
Sources
50%
Confidence
Long-term
Relevance
10/24/2026
First Seen
Sources
Related Entities
Related Claims
VerifiedThe underlying mechanism of Tool Use is that developers pre-define the name, description, and parameter structure (Schema) of tools, and the model determines during inference when and which tool to call and outputs structured invocation instructions.70% similarVerifiedFunction Calling (Tool Use) is a standardized mechanism for large models to invoke external tools, where developers pre-declare tool names, descriptions, and parameter schemas, and the model autonomously determines when to make a call.70% similarUnverifiedThe approach forces Claude to return structured JSON (containing reply, confidence, source_ids) by defining a tool answerTool and pointing tool_choice at it.68% similarUnverifiedThe tool definitions themselves also consume context tokens, and the model's understanding of a tool depends on the clarity of its description.68% similarUnverifiedAnthropic's Claude model natively supports the Tool Use protocol, where the model generates structured tool call requests in its responses.68% similar
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