Slack Messaging Best Practices

When to Use

slack_send_message

slack_send_message_draft

slack_create_canvas

Slack Formatting (mrkdwn)

*text*

_text_

~text~

`code`

```code```

> text

<url|display text>

<@U123456>

<#C123456>

- item

• item

1. item

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.