---
title: "Add Messages"
method: POST
path: "/v1/threads/{thread_id}/messages"
tags: ["assistants"]
---

# Add Messages

`POST /v1/threads/{thread_id}/messages`

Create a message.

API Reference - https://platform.openai.com/docs/api-reference/messages/createMessage

## Path parameters

- `thread_id` string, required

## Response `200`

Successful Response

- unknown

## Other responses

- `422` — Validation Error

## Changes

- **2026-09-18** `082b5fabd909` — 2 info
  - added the optional property `detail/items/ctx` to the response with the `422` status
  - added the optional property `detail/items/input` to the response with the `422` status

[Change history](https://skmtc.dev/flock/apis/litellm-api/changes/v1/threads/:thread_id/messages/post.md)

---

[API](https://skmtc.dev/flock/apis/litellm-api.md) · [All operations](https://skmtc.dev/flock/apis/litellm-api/llms.txt) · [OpenAPI document](https://skmtc.dev/flock/apis/litellm-api/revisions/c71315002afa?raw)