Slack Messaging
- 3.2k installs
- 23.1k repo stars
- Updated July 28, 2026
- anthropics/knowledge-work-plugins
A skill for composing Slack messages with correct mrkdwn syntax, structure, and thread versus channel etiquette.
About
Slack Messaging Best Practices teaches agents to compose effective Slack messages using mrkdwn, which differs from standard Markdown. Formatting rules cover bold with single asterisks, italic with underscores, strikethrough with tildes, inline and block code with backticks, quotes with angle brackets, and links as url|display text in angle brackets. Common mistakes to avoid include double-asterisk bold, Markdown headers, bracket-paren links, and horizontal rules that Slack does not render. Message structure guidance says lead with the point in the first line, keep messages to one to three short paragraphs, use line breaks generously, convert three or more items into bullet lists, and bold names, dates, deadlines, and action items. Thread etiquette recommends replying in threads for specific messages, using reply_broadcast only when everyone needs the reply, posting new topics in the channel, and continuing existing conversations in the original thread. Tone should match the channel, with emoji reactions suggested for simple acknowledgments when MCP tools cannot add reactions directly.
- Slack mrkdwn uses *bold* not **bold** and <url|text> not [text](url)
- No Markdown headers or horizontal rules in Slack messages
- Lead with the point; keep messages to 1-3 short paragraphs
- Reply in threads for specific messages; broadcast only when needed
- Bold key names, dates, deadlines, and action items for scanning
Slack Messaging by the numbers
- 3,161 all-time installs (skills.sh)
- +121 installs in the week ending Jul 28, 2026 (Skillselion tracking)
- Ranked #164 of 3,301 Productivity & Planning skills by installs in the Skillselion catalog
- Security screen: MEDIUM risk (skills.sh audit)
- Data as of Jul 28, 2026 (Skillselion catalog sync)
slack-messaging capabilities & compatibility
- Capabilities
- apply mrkdwn bold, italic, code, quote, and link · avoid markdown headers, double asterisk bold, an · structure messages with lead point, short paragr · choose thread replies versus channel posts appro · bold names, dates, deadlines, and action items f
- Works with
- slack
- Runs
- Hosted SaaS
- Pricing
- Free
npx skills add https://github.com/anthropics/knowledge-work-plugins --skill slack-messagingAdd your badge
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| Installs | 3.2k |
|---|---|
| repo stars | ★ 23.1k |
| Security audit | 3 / 3 scanners passed |
| Last updated | July 28, 2026 |
| Repository | anthropics/knowledge-work-plugins ↗ |
How do agents draft Slack messages that render correctly instead of using Markdown syntax Slack does not support?
Compose well-formatted Slack messages using mrkdwn syntax with correct bold, links, lists, and thread versus channel etiquette.
Who is it for?
Anyone drafting Slack messages via agents, including slack_send_message and slack_create_canvas tool calls.
Skip if: Skip when the task is Slack app development, webhook integration, or channel administration rather than message composition.
When should I use this skill?
Use when composing, drafting, or helping write a Slack message with slack_send_message or related Slack MCP tools.
What you get
Short, scannable Slack messages with valid mrkdwn, bold key info, and appropriate thread or channel placement.
- formatted Slack messages
- canvas drafts
By the numbers
- Covers 3 Slack tool integrations: send_message, send_message_draft, create_canvas
Files
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>` |
| 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.
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Use slack-messaging for mrkdwn composition; use the discord skill when formatting messages for Discord channels instead.
FAQ
How do I make bold text in Slack?
Use single asterisks: *bold*. Double asterisks **bold** do not work in Slack mrkdwn.
How do I format links in Slack?
Use angle brackets with a pipe: <https://example.com|display text>. Standard Markdown link syntax does not render.
When should I reply in a thread versus the channel?
Reply in threads for specific messages. Post in the channel for new topics, announcements, or whole-group questions.
Is Slack Messaging safe to install?
skills.sh reports 3 of 3 security scanners passed. Review the Security Audits panel on this page before installing in production.