slack-rich-output
Slack Rich Output
Slack-native formatting for messages using mrkdwn syntax and Block Kit.
CRITICAL: Two Markup Systems
Slack has two completely different markup syntaxes. Using the wrong one is the most common formatting mistake.
| System | Used In | Bold | Link | Heading |
|---|---|---|---|---|
| Slack mrkdwn | text field, text objects (type: "mrkdwn"), section fields |
*bold* |
<url|text> |
Not supported |
| Standard Markdown | markdown block only |
**bold** |
[text](url) |
# Heading |
Standard Markdown syntax (**bold**, [text](url), # Heading) renders as literal text in mrkdwn contexts. Slack mrkdwn syntax (*bold*, <url|text>) renders as literal text in markdown blocks. Never mix them.
The markdown block is designed for AI app output — it renders standard Markdown natively in Slack. However, it only works in Messages (not Modals or Home tabs), has a 12,000 character cumulative limit per payload, and does not support syntax highlighting, horizontal rules, tables, or task lists. block_id is ignored.
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