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.
Slack Formatting (mrkdwn)
Slack uses its own markup syntax called mrkdwn, which differs from standard Markdown. Always use mrkdwn when composing Slack messages:
| Format | Syntax | Notes | |
|---|---|---|---|
| Bold | *text* | Single asterisks, NOT double | |
| Italic | _text_ | Underscores | |
| Strikethrough | ~text~ | Tildes | |
| Code (inline) | ` code ` | Backticks | |
| Code block | ``` `code` ``` | Triple backticks | |
| Quote | > text | Angle bracket | |
| Link | `<url\ | display text>` | Pipe-separated in angle brackets |
| User mention | <@U123456> | User ID in angle brackets | |
| Channel mention | <#C123456> | Channel ID in angle brackets | |
| Bulleted list | - item or • item | Dash or bullet character | |
| Numbered list | 1. item | Number followed by period |
Common Mistakes to Avoid
- Do NOT use
**bold**(double asterisks) — Slack uses*bold*(single asterisks) - Do NOT use
## headers— Slack does not support Markdown headers. Use*bold text*on its own line instead. - Do NOT use
[text](url)for links — Slack uses<url|text>format - Do NOT use
---for horizontal rules — Slack does not render these
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 —
#generalis 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.