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Prompt

what API should I use for tool calling and JSON output

Artificial Intelligence / AI Platforms1 observationLast seen Oct 8, 2026

Latest observation

Oct 8, 2026OpenAI APIWeb search: off

Use the Responses API.

It’s the best current API for both:

  • Tool calling — letting the model decide when to call your tools/functions
  • Structured JSON output — getting reliably schema-shaped JSON back

Why Responses API

  • It’s the newer, more flexible API
  • It supports:
    • tools for function calling
    • response_format / structured outputs for JSON
    • multimodal inputs in one place

When to use what

  • Use Responses API if you want:

    • tool calling
    • JSON outputs
    • a single API for most workflows

  • Use Chat Completions API only if:

    • you’re maintaining older code
    • you already have a working integration and don’t want to migrate yet

Example use cases

  • “Call my weather API if needed, then return JSON summary” → Responses API
  • “Return only valid JSON matching this schema” → Responses API

If you want, I can give you:

  1. a minimal Python example,
  2. a Node.js example, or
  3. an example that combines tool calling + JSON schema output.

Brands

Responses ApiChat Completions Api

Observation history

How did Obsurfable measure this prompt?

Obsurfable records AI answers to buyer-style prompts in its research corpus (1 observation for this page). Metrics are distributions over observations, not a single static ranking.

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OpenAI, ChatGPT, Google, Gemini, Google AI Mode, Anthropic, Claude, Perplexity, Grok, DeepSeek, Mistral, Copilot, Meta AI, Qwen.

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