---
title: "Changes to Create a message (Anthropic Messages API)"
method: POST
path: "/v1/messages"
---

# Changes to Create a message (Anthropic Messages API)

`POST /v1/messages`

> Every recorded change to this operation, newest first.

## Timeline

Changed in 8 of 102 revisions.

- **2026-10-21** `55b5f7973ff4`: 1 info
- **2026-10-03** `d077e0a45fc6`: 2 info
- **2026-09-25** `bc48c7850107`: 1 info
- **2026-09-08** `3a3732a1e621`: 10 info
- **2026-09-07** `6d038b14f291`: 5 info
- **2026-08-22** `496ff50bdfef`: 9 info
- **2026-08-14** `e31b805bf9ac`: 2 info
- **2026-05-22** `4473702da82e`: 1 info

## Changes

- **2026-10-21** `55b5f7973ff4`: 1 info
  - added the new optional request property `tools/items/defer_loading`
- **2026-10-03** `d077e0a45fc6`: 2 info
  - added the new optional request property `output_config`
  - added the new optional request property `output_format`
- **2026-09-25** `bc48c7850107`: 1 info
  - added the new optional request property `tools/items/strict`
- **2026-09-08** `3a3732a1e621`: 10 info
  - added the new optional request property `messages/items/content/oneOf[subschema #2]/items/data`
  - added the new optional request property `messages/items/content/oneOf[subschema #2]/items/signature`
  - added the new optional request property `system/oneOf[subschema #2]/items/data`
  - added the new optional request property `system/oneOf[subschema #2]/items/signature`
  - added the optional property `anyOf[#/components/schemas/anthropicapi.SSEContentBlockStartEvent]/content_block/data` to the response with the `200` status (media type: text/event-stream)
  - added the optional property `anyOf[#/components/schemas/anthropicapi.SSEContentBlockStartEvent]/content_block/signature` to the response with the `200` status (media type: text/event-stream)
  - added the optional property `anyOf[#/components/schemas/anthropicapi.SSEMessageStartEvent]/message/content/items/data` to the response with the `200` status (media type: text/event-stream)
  - added the optional property `anyOf[#/components/schemas/anthropicapi.SSEMessageStartEvent]/message/content/items/signature` to the response with the `200` status (media type: text/event-stream)
  - added the optional property `content/items/data` to the response with the `200` status (media type: application/json)
  - added the optional property `content/items/signature` to the response with the `200` status (media type: application/json)
- **2026-09-07** `6d038b14f291`: 5 info
  - added the new optional request property `messages/items/content/oneOf[subschema #2]/items/extra_content`
  - added the new optional request property `system/oneOf[subschema #2]/items/extra_content`
  - added the optional property `anyOf[#/components/schemas/anthropicapi.SSEContentBlockStartEvent]/content_block/extra_content` to the response with the `200` status (media type: text/event-stream)
  - added the optional property `anyOf[#/components/schemas/anthropicapi.SSEMessageStartEvent]/message/content/items/extra_content` to the response with the `200` status (media type: text/event-stream)
  - added the optional property `content/items/extra_content` to the response with the `200` status (media type: application/json)
- **2026-08-22** `496ff50bdfef`: 9 info
  - added the optional property `anyOf[#/components/schemas/anthropicapi.SSEErrorEvent]/error/provider` to the response with the `200` status
  - added the optional property `error/provider` to the response with the `400` status (media type: application/json)
  - added the optional property `error/provider` to the response with the `400` status (media type: text/event-stream)
  - added the optional property `error/provider` to the response with the `401` status (media type: application/json)
  - added the optional property `error/provider` to the response with the `401` status (media type: text/event-stream)
  - added the optional property `error/provider` to the response with the `429` status (media type: application/json)
  - added the optional property `error/provider` to the response with the `429` status (media type: text/event-stream)
  - added the optional property `error/provider` to the response with the `502` status (media type: application/json)
  - added the optional property `error/provider` to the response with the `502` status (media type: text/event-stream)
- **2026-08-14** `e31b805bf9ac`: 2 info
  - added the new optional request property `cache_control`
  - added the new optional request property `tools/items/cache_control`
- **2026-05-22** `4473702da82e`: 1 info
  - endpoint added

---

[Operation](https://skmtc.dev/enterpilot/apis/gomodel-api/docs/v1/messages/post.md) - [API](https://skmtc.dev/enterpilot/apis/gomodel-api.md) - [Page](https://skmtc.dev/enterpilot/apis/gomodel-api/changes/v1/messages/post)