Tool Calling
Also called Function calling, Tool use
Tool calling lets a model request an operation through a structured interface. The application executes the request and makes the result available to the model.
[Anthropic]In practice · hypothetical example
A model requests an order lookup with an order number; the application returns the matching status.
[Anthropic]A little deeper
Describing a tool and requesting it are different from actually executing it. [Anthropic]
Has a requested tool already run?
Sources & editorial notes
Evidence: supported. Primary-source support for this scoped entry; publication approved by the project owner.
- Building effective agents ↗ (opens in new tab)Anthropic · 2024-12-19
Relevant section: What are agents?; Building blocks; Agents; Appendix 2
Last editorial review: 2026-09-13 by project-owner.
First observed in this corpus: Unknown.
Revision history
Revision 2 · Created 2026-09-12 · Updated 2026-09-13
Project owner approved the current content for publication. Existing evidence scope and limitations remain applicable.