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This page is an outline. It describes what will be covered and is not yet complete technical documentation.

Some inference servers expose an Anthropic-compatible Messages API alongside or instead of an OpenAI-compatible one. The two express similar capabilities with different request structures, and the differences matter when writing portable clients.

This page covers the shape conceptually; the service-specific details are in the llm- inference user guide.

What you will learn

  • The structure of a Messages API request and response.
  • How system prompts and message roles are represented.
  • How tool use is expressed compared with the OpenAI-compatible surface.
  • What to account for when supporting both APIs from one client.

This page is an outline. The subsections below are the planned structure; they are filled in as the handbook is written.

The Messages API shape

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Roles and system prompts

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Content blocks

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Tool use

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Streaming

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Supporting both API families

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