slack-messaging

SKILL.md

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 — #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.