---
title: "Replies to a message in a Slack thread."
method: POST
path: "/replyMessage"
tags: ["message"]
---

# Replies to a message in a Slack thread.

`POST /replyMessage`

Replies to an existing message in a Slack thread.

## Request body

- object
  - `body` object — Body of the replyMessage sls call
    - `arguments` object, required
      - `channelId` string, required — The ID of the channel where the message is. Channel IDs start with 'C'.
      - `thread_ts` string, required — The timestamp of the message to reply to, which establishes the thread.
      - `text` string, required — The text of the reply.
      - `username` string — Optional custom username for the message.
      - `icon_url` string — Optional URL to an image to use as the icon for the message.

## Response `200`

Successful response

- object
  - `ok` boolean, required — true if the request was successful.
  - `channel` string, required — The ID of the channel where the message was posted.
  - `ts` string, required — The timestamp of the message.
  - `message` object, required — An object containing the details of the sent message.

## Other responses

- `400` — Bad Request - The request was invalid or cannot be served.
- `500` — Internal Server Error - The server encountered an unexpected condition that prevented it from fulfilling the request.

## Changes

- **2025-07-23** `a34e4f697384` — 2 info
  - added the new optional request property `body/arguments/icon_url`
  - added the new optional request property `body/arguments/username`
- **2025-07-15** `c28a413c6b00` — 4 breaking, 7 warning, 3 info
  - the response property `error` became optional for the status `400`
  - the response property `error` became optional for the status `500`
  - the response property `ok` became optional for the status `400`
  - the response property `ok` became optional for the status `500`
  - …10 more
- **2025-07-10** `b883cbfe46f6` — 1 info
  - endpoint added
- **2025-06-20** `37c50ff8be3a` — 1 breaking
  - api path removed without deprecation

[Change history](https://skmtc.dev/microfox-ai/apis/slack-d/changes/replyMessage/post.md)

---

[API](https://skmtc.dev/microfox-ai/apis/slack-d.md) · [All operations](https://skmtc.dev/microfox-ai/apis/slack-d/llms.txt) · [OpenAPI document](https://skmtc-service-production.skmtc.workers.dev/v1/apis/microfox-ai/slack-d/revisions/cd0edf0c2cdf/schema)