conversations_add_message
Post messages to Slack channels, threads, or direct messages using markdown or plain text formatting. Requires OAuth authentication and channel targeting for secure message delivery.
Instructions
Posts a message to a channel, thread, or DM. Supports markdown and plain text. NOTE: Disabled by default for safety - set SLACK_MCP_ADD_MESSAGE_TOOL environment variable to enable.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| accessToken | Yes | Slack OAuth token (xoxp-... or xoxb-...) with chat:write scope | |
| channel_id | Yes | Target channel ID, name (#general), or DM (@username) | |
| thread_ts | No | Thread timestamp; omit to post to channel directly | |
| payload | Yes | Message content to post | |
| content_type | No | Content format (default: text/markdown) |
Input Schema (JSON Schema)
{
"properties": {
"accessToken": {
"description": "Slack OAuth token (xoxp-... or xoxb-...) with chat:write scope",
"type": "string"
},
"channel_id": {
"description": "Target channel ID, name (#general), or DM (@username)",
"type": "string"
},
"content_type": {
"description": "Content format (default: text/markdown)",
"type": "string"
},
"payload": {
"description": "Message content to post",
"type": "string"
},
"thread_ts": {
"description": "Thread timestamp; omit to post to channel directly",
"type": "string"
}
},
"required": [
"accessToken",
"channel_id",
"payload"
],
"type": "object"
}