function-calling agent-patterns json-schema api-integration python

Claude tool use follows request-execute-return loop

Define tools as JSON schema, handle tool_use blocks in responses, execute functions, return results—repeat until end_turn.

Summary

Tool use replaces manual API orchestration for Claude integrations, reducing boilerplate and enabling reliable multi-step agent workflows. Precise schema definition is the critical control point for production deployments.

Why it matters

Implementation verdict

Replaces ad-hoc Claude integration patterns. Requires JSON schema definitions, response parsing for tool_use blocks, and execution handlers. Ready to implement now—the pattern is stable and documented with working Python/TypeScript examples.

Sources

1.Tool use (also called function calling) lets Claude request execution of external functions during a conversation — search engines, calculators, databases, APIs
2.Every tool use interaction follows the same cycle: You define tools — name, description, input schema
3.This cycle repeats until Claude returns stop_reason: "end_turn" with no tool use

Dev Signal

Get briefs like this in your inbox — free, every weekday.

100+ sources compressed into one 4-minute read. Ranked, cited, implementation-ready.

Read the full issue →All briefs