Slack Messaging

Slack Messaging Best Practices

This skill provides guidance for composing well-formatted, effective Slack messages.

When to Use

Apply this skill whenever composing, drafting, or helping the user write a Slack message — including when using slack_send_message, slack_send_message_draft, or slack_create_canvas.

Formatting

Slack MCP accepts standard markdown. Use familiar markdown syntax when composing messages:

| Format | Syntax | |--------|--------| | Bold | **text** | | Italic | _text_ or *text* | | Strikethrough | ~text~ | | Code (inline) | ` code | | Code block | `code` | | Quote | > text | | Link | [display text](url) | | Bulleted list | - item | | Numbered list | 1. item` |

Not supported:

• Tables
• Headers (#, ##, etc.)
• Images via markdown ()

Message Structure Guidelines

• Lead with the point. Put the most important information in the first line. Many people read Slack on mobile or in notifications where only the first line shows.
• Keep it short. Aim for 1-3 short paragraphs. If the message is long, consider using a Canvas instead.
• Use line breaks generously. Walls of text are hard to read. Separate distinct thoughts with blank lines.
• Use bullet points for lists. Anything with 3+ items should be a list, not a run-on sentence.
• Bold key information. Use *bold* for names, dates, deadlines, and action items so they stand out when scanning.

Thread vs. Channel Etiquette

• Reply in threads when responding to a specific message to keep the main channel clean.
• Use reply_broadcast (also post to channel) only when the reply contains information everyone needs to see.
• Post in the channel (not a thread) when starting a new topic, making an announcement, or asking a question to the whole group.
• Don't start a new thread to continue an existing conversation — find and reply to the original message.

Tone and Audience

• Match the tone to the channel — #general is usually more formal than #random.
• Use emoji reactions instead of reply messages for simple acknowledgments (though note: the MCP tools can't add reactions, so suggest the user do this manually if appropriate).
• When writing announcements, use a clear structure: context, key info, call to action.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: slackapi
• Source: slackapi/slack-mcp-plugin
• License: MIT

Install and usage instructions live in the source repository linked above.