slack-message-formatter

Slack Message Formatter

Format messages for Slack with pixel-perfect accuracy. Converts Markdown to Slack-compatible output with two delivery paths:

1. Copy-paste — Rich HTML that preserves formatting when pasted into Slack's compose box
2. API/Webhook — Slack mrkdwn syntax for bots, automation, and CI/CD

When to Use This Skill

• User asks to write a Slack message, announcement, or notification
• User asks to format something "for Slack"
• User wants to preview how a message will look in Slack
• User wants to send a message via Slack webhook
• User has Markdown content they want to share in Slack

What This Skill Does

1. Generates content in Markdown — Claude writes the message in standard Markdown, its native format
2. Converts to Rich HTML — Transforms Markdown into rich HTML that preserves formatting when pasted into Slack's compose box
3. Converts to Slack mrkdwn — Transforms Markdown into Slack's proprietary mrkdwn syntax for API/webhook delivery
4. Generates a Slack-themed preview — Creates an HTML preview page styled like the Slack UI and opens it in the browser
5. Copies to clipboard — Automatically copies the rich HTML to the system clipboard for one-step paste into Slack

How to Use

Basic Usage

Write a Slack message announcing our Q2 product launch

Format this for Slack: We shipped 3 new features this week...

Create a Slack announcement for the engineering team about the new CI pipeline

Webhook/API Delivery

Send a deploy notification to Slack via webhook

Formatting Features

The converter handles all Markdown features and translates them correctly for Slack:

• Bold, italic, strikethrough, inline code
• Links and headings (converted to bold in Slack)
• Tables (rich HTML tables for paste, code blocks for API)
• Task lists with emoji checkboxes
• Nested lists and blockquotes
• Code blocks with syntax highlighting
• Slack mentions (<@U012AB3CD>, <!here>, <!channel>)
• 150+ emoji shortcodes converted to Unicode

Example

User: "Write a Slack message announcing our new feature"

Output (opened as a Slack-themed preview in the browser + copied to clipboard):

The preview shows a pixel-perfect Slack UI rendering. The user pastes directly into Slack with Cmd+V / Ctrl+V and the formatting is preserved.

User: "Send a deploy notification to our #deploys channel via webhook"

Output (sent via mrkdwn to the configured webhook):

*:rocket: Deploy Successful*

*Service:* payment-api
*Version:* v2.5.1
*Environment:* production
*Duration:* 47s

:white_check_mark: All health checks passing

Configuration

| Env Variable | Default | Description |

|-------------|---------|-------------|

| SLACK_FORMATTER_CLIPBOARD | true | Set to false to disable auto-clipboard copy |

| SLACK_FORMATTER_PREVIEW_DIR | /tmp/slack-formatter | Directory for preview HTML files |

| CCH_SLA_WEBHOOK | (none) | Slack webhook URL for sending messages |

Tips

• Always let the converter handle the Markdown-to-Slack translation; never write mrkdwn or HTML by hand
• Slack mentions (<@U...>, <#C...>, <!here>) can be included directly in the Markdown
• Tables work beautifully via the copy-paste path; for API delivery they become code blocks (Slack has no table syntax)
• Preview files are timestamped so you can revisit them from conversation history