This listing is posted by the APIs.io catalog. APIs.io does not own or sell this API; we get access to it from the provider, Anthropic.
The Anthropic Messages API lets you send a structured list of input messages with text and/or image content, and the model generates the next message in the conversation. The records list support for text, images, tool use, extended thinking, streaming, structured outputs, prompt caching, compaction, and an advisor tool that pairs an executor model with a higher-intelligence advisor model. Developers building chat, assistant, or agent features on Claude models would use it. The base URL is https://api.anthropic.com/v1.
Published for it: Documentation, OpenAPI, AsyncAPI, JSONSchema, JSONLD, APIsJSON and Arazzo.
The provider, Anthropic, has a Kin Score of 88.8 (exemplar band) and an Agent Readiness score of 46.7 (agent-ready band, scored 2026-10-17). Authentication is by x-api-key header, with a required anthropic-version date header.
Pricing: set by the provider. The catalog classes access as paid.
Condition: a live hosted API, you call the provider's endpoint, listed in the APIs.io catalog.
Catalog listing: https://apis.io/apis/anthropic/anthropic-messages-api/ Provider: https://www.anthropic.com/