Slack Messaging
Compose Slack posts and canvases that render correctly with mrkdwn instead of broken Markdown.
Overview
Slack Messaging is an agent skill most often used in Grow (also Build integrations and Operate support) that formats Slack-ready copy using mrkdwn instead of standard Markdown.
Install
npx skills add https://github.com/anthropics/knowledge-work-plugins --skill slack-messagingWhat is this skill?
- Maps standard Markdown habits to Slack mrkdwn (single-asterisk bold, underscore italic, pipe links)
- Covers lists, quotes, code blocks, and user/channel mention syntax
- Explicit anti-patterns: no ## headers, no **double-asterisk** bold
- Triggered for slack_send_message, slack_send_message_draft, and slack_create_canvas flows
- mrkdwn formatting table with 10+ syntax rows
- 3 named Slack tool triggers: send, draft, canvas
Adoption & trust: 2k installs on skills.sh; 19.6k GitHub stars; 3/3 security scanners passed (skills.sh audits).
What problem does it solve?
You want the agent to post to Slack but its drafts use Markdown conventions that Slack does not render.
Who is it for?
Indie builders automating status posts, incident notes, or handoffs into Slack from an agent workflow.
Skip if: Long-form docs meant for Notion or GitHub README only, or channels where you never use Slack send/canvas tools.
When should I use this skill?
Composing, drafting, or helping the user write a Slack message—including slack_send_message, slack_send_message_draft, or slack_create_canvas.
What do I get? / Deliverables
Messages and canvases use valid mrkdwn so bold, links, and lists display correctly when sent through Slack tools.
- Slack-ready message or canvas body in mrkdwn
Recommended Skills
Journey fit
Spans multiple journey phases - primary shelf plus alternate fits below.
Team and customer Slack updates are most common once the product is live and you are coordinating support and ops. Support and async team comms are the primary shelf for message-formatting guidance tied to Slack send tools.
Where it fits
Turn a customer-reply draft into mrkdwn before the agent sends it in a support channel.
Validate mrkdwn in integration tests that exercise slack_send_message_draft.
How it compares
Formatting guidance for Slack mrkdwn—not a Slack OAuth app or standalone messaging MCP by itself.
Common Questions / FAQ
Who is slack-messaging for?
Solo and indie builders whose agents call Slack send or canvas tools and need correct mrkdwn without re-editing every draft.
When should I use slack-messaging?
Use it while composing any Slack message in Grow support threads, Operate incident channels, or Build integration tests that hit slack_send_message or slack_create_canvas.
Is slack-messaging safe to install?
It is text-formatting guidance only; review the Security Audits panel on this page before installing the parent plugin bundle.
SKILL.md
READMESKILL.md - 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`. ## 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.