---
title: "Create Message Route"
method: POST
path: "/api/threads/{thread_id}/messages/"
tags: ["message"]
---

# Create Message Route

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

Creates a new message.

## Path parameters

- `thread_id` string, uuid, required

## Request body

- MessageCreateInput
  - `role` 'user' | 'assistant', required
  - `content` string, required
  - `metadata` MessageMetadataInput, required
    - `trustworthiness_score` number, nullable
    - `trustworthiness_explanation` string, nullable
    - `is_expert_answer` boolean, nullable
    - `is_bad_response` boolean, nullable
    - `citations` string[], nullable
    - `scores` ResponseScoreMetadataInput
      - `trustworthiness` EvalResult
        - `score` number, nullable
        - `is_bad` boolean, nullable
        - `log` EvalLog
          - `explanation` string, required
      - `response_helpfulness` EvalResult
        - `score` number, nullable
        - `is_bad` boolean, nullable
        - `log` EvalLog
          - `explanation` string, required
      - `context_sufficiency` EvalResult
        - `score` number, nullable
        - `is_bad` boolean, nullable
        - `log` EvalLog
          - `explanation` string, required
      - `response_groundedness` EvalResult
        - `score` number, nullable
        - `is_bad` boolean, nullable
        - `log` EvalLog
          - `explanation` string, required
      - `query_ease` EvalResult
        - `score` number, nullable
        - `is_bad` boolean, nullable
        - `log` EvalLog
          - `explanation` string, required

## Response `201`

Successful Response

- Message
  - `thread_id` string, uuid, required
  - `role` 'user' | 'assistant', required
  - `content` string, required
  - `metadata` MessageMetadataOutput, required
    - `trustworthiness_score` number, nullable
    - `trustworthiness_explanation` string, nullable
    - `is_expert_answer` boolean, nullable
    - `is_bad_response` boolean, nullable
    - `citations` string[], nullable
    - `scores` ResponseScoreMetadataOutput
      - `trustworthiness` EvalResult
        - `score` number, nullable
        - `is_bad` boolean, nullable
        - `log` EvalLog
          - `explanation` string, required
      - `response_helpfulness` EvalResult
        - `score` number, nullable
        - `is_bad` boolean, nullable
        - `log` EvalLog
          - `explanation` string, required
      - `context_sufficiency` EvalResult
        - `score` number, nullable
        - `is_bad` boolean, nullable
        - `log` EvalLog
          - `explanation` string, required
      - `response_groundedness` EvalResult
        - `score` number, nullable
        - `is_bad` boolean, nullable
        - `log` EvalLog
          - `explanation` string, required
      - `query_ease` EvalResult
        - `score` number, nullable
        - `is_bad` boolean, nullable
        - `log` EvalLog
          - `explanation` string, required
  - `id` string, uuid, required
  - `created_at` string, date-time, required
  - `updated_at` string, date-time, required
  - `deleted_at` string, date-time, nullable

## Other responses

- `422` — Validation Error

## Changes

- **2025-04-15** `f22c2d6c16f0` — 1 breaking, 3 info
  - removed `#/components/schemas/MessageMetadata` from the `metadata` request property `anyOf` list
  - added `#/components/schemas/MessageMetadata-Input` to the `metadata` request property `anyOf` list
  - added `#/components/schemas/ResponseScoreMetadata-Output` to the `metadata/scores` response property `anyOf` list for the response status `201`
  - removed `#/components/schemas/ResponseScoreMetadata` from the `metadata/scores` response property `anyOf` list for the response status `201`
- **2025-04-14** `b890eea39144` — 6 info
  - added the new optional request property `metadata/anyOf[subschema #1: MessageMetadata]/is_bad_response`
  - added the new optional request property `metadata/anyOf[subschema #1: MessageMetadata]/is_expert_answer`
  - added the new optional request property `metadata/anyOf[subschema #1: MessageMetadata]/scores`
  - added the optional property `metadata/is_bad_response` to the response with the `201` status
  - …2 more
- **2025-01-15** `92f517edd77d` — 2 info
  - added the new optional request property `metadata/anyOf[subschema #1: MessageMetadata]/trustworthiness_explanation`
  - added the optional property `metadata/trustworthiness_explanation` to the response with the `201` status
- …earlier changes not shown

[Full history](https://skmtc.dev/cleanlab/apis/agility/changes/api/threads/:thread_id/messages/post.md)

---

[API](https://skmtc.dev/cleanlab/apis/agility.md) · [All operations](https://skmtc.dev/cleanlab/apis/agility/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/cleanlab/agility/revisions/f22c2d6c16f0/schema)