Guidance for composing well-formatted, effective Slack messages using mrkdwn syntax

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 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.

slack-messaging