Message Tools

Tools for sending, reading, searching, and managing messages in Mattermost.

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post_message

Post a message to a Mattermost channel.

Send text messages with Markdown support. Use root_id to reply in a thread. Use file_ids to attach uploaded files. Use attachments for rich formatted content with colors, fields, and images. To read all messages in a thread, use get_thread.

Example prompts

• "Send 'Hello team!' to #general"
• "Post a status update in the engineering channel"
• "Reply to that message in the thread"
• "Send a message with a red alert attachment"

Annotations

Hint	Value
destructiveHint	false

Parameters

Name	Type	Required	Default	Description
channel_id	string	✓	—	Channel ID to post to
message	string	✓	—	Message content, supports Markdown (1-16383 chars)
root_id	string	—	—	Root post ID for threading
file_ids	array	—	—	File IDs to attach (from upload_file)
attachments	array	—	—	Rich message attachments (see Attachments section)

Attachment Examples

// Status alert
{"color": "danger", "title": "Build Failed", "text": "Tests failed on main"}

// Success notification
{"color": "good", "title": "Deployed", "text": "v1.2.3 is live"}

// With structured fields
{
  "title": "Ticket #123",
  "fields": [
    {"title": "Status", "value": "Open", "short": true},
    {"title": "Priority", "value": "High", "short": true}
  ]
}

Returns

Post object with id, channel_id, message, create_at, user_id.

Mattermost API

POST /api/v4/posts

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get_channel_messages

Get recent messages from a channel.

Returns messages in reverse chronological order (newest first). Use for reading channel conversation history. For searching messages by keywords across channels, use search_messages instead.

Example prompts

• "Show me the last 10 messages in #general"
• "What's the recent conversation in engineering?"
• "Read the channel history"

Annotations

Hint	Value
readOnlyHint	true
idempotentHint	true

Parameters

Name	Type	Required	Default	Description
channel_id	string	✓	—	Channel ID
page	integer	—	0	Page number (0-indexed)
per_page	integer	—	60	Results per page (1-200)

Returns

Object with posts (map of post objects) and order (array of post IDs).

Mattermost API

GET /api/v4/channels/{channel_id}/posts

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search_messages

Search for messages matching specific criteria across channels.

Searches message content within a team. Supports Mattermost search syntax (from:, in:, before:, after:). For simply reading recent channel messages, use get_channel_messages instead.

Example prompts

• "Search for messages about the deployment"
• "Find messages from @john about the bug"
• "Search for 'API error' in the last week"

Annotations

Hint	Value
readOnlyHint	true
idempotentHint	true

Parameters

Name	Type	Required	Default	Description
team_id	string	✓	—	Team ID to search in
terms	string	✓	—	Search terms, supports Mattermost syntax (1-512 chars)
is_or_search	boolean	—	false	Use OR instead of AND for multiple terms

Returns

Object with posts (map of matching post objects) and order (array of post IDs).

Mattermost API

POST /api/v4/teams/{team_id}/posts/search

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update_message

Edit an existing message.

Can only edit your own messages (unless admin). The message will show as edited. Original content is replaced; edit history is not preserved. Use attachments to add or update rich formatted content.

Example prompts

• "Edit my last message to say..."
• "Fix the typo in that message"
• "Update the announcement"
• "Add an attachment to that message"

Annotations

Hint	Value
destructiveHint	false

Parameters

Name	Type	Required	Default	Description
post_id	string	✓	—	Post ID to edit
message	string	✓	—	New message content (1-16383 chars)
attachments	array	—	—	Rich message attachments (see post_message for examples)

Returns

Updated post object with id, message, edit_at.

Mattermost API

PUT /api/v4/posts/{post_id}

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delete_message

Delete a message permanently.

Can only delete your own messages (unless admin). Deleted messages cannot be recovered. All reactions and thread context will be lost.

Example prompts

• "Delete that message"
• "Remove my last post"

Annotations

Hint	Value
destructiveHint	true

Parameters

Name	Type	Required	Default	Description
post_id	string	✓	—	Post ID to delete

Returns

None

Mattermost API

DELETE /api/v4/posts/{post_id}

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Attachment Format

Rich message attachments allow formatted content with colors, fields, author info, and images. Based on Slack attachment format.

Attachment Fields

Field	Type	Description
fallback	string	Plain-text summary for notifications
color	string	Left border: good, warning, danger, or #RRGGBB hex
pretext	string	Text above attachment
text	string	Main content (supports Markdown)
author_name	string	Author display name
author_link	string	Author profile URL (requires author_name)
author_icon	string	Author avatar URL
title	string	Attachment title
title_link	string	Title hyperlink URL (requires title)
fields	array	Structured data fields (see below)
image_url	string	Main image URL
thumb_url	string	Thumbnail image URL (75x75)
footer	string	Footer text (max 300 chars)
footer_icon	string	Footer icon URL

Field Object

Field	Type	Description
title	string	Field label/header
value	string/number	Field content
short	boolean	Display inline with other short fields (default: false)

Full Example

{
  "color": "#FF5733",
  "pretext": "New deployment notification",
  "author_name": "CI/CD Bot",
  "author_icon": "https://example.com/bot-icon.png",
  "title": "Production Deployment",
  "title_link": "https://github.com/org/repo/releases/v1.2.3",
  "text": "Version 1.2.3 deployed successfully",
  "fields": [
    {"title": "Environment", "value": "Production", "short": true},
    {"title": "Duration", "value": "45s", "short": true},
    {"title": "Changes", "value": "5 commits", "short": true},
    {"title": "Author", "value": "@developer", "short": true}
  ],
  "footer": "Deployed via GitHub Actions",
  "ts": 1706886000
}