Slack Block Kit Formatting Skill

This skill teaches agents to format Slack messages using Block Kit—a JSON-based UI framework for building rich, interactive messages.

When to Apply This Skill

Apply when:

Sending Slack messages via MCP tools
Creating notifications, alerts, or status updates
Building interactive messages with buttons or menus
Formatting EOD/EOW reports for Slack
Any message that should look professional

MCP Tools

Server:

user-mcp-config-2mgoji

(Composio) Tool:

SLACK_SEND_MESSAGE

json

{
  "channel": "C12345678",
  "text": "Fallback text for notifications",
  "blocks": [ ... ]
}

Important: Always include top-level

text

as notification fallback.

Architecture

Message Payload
└── blocks[] (layout containers, max 50)
    └── Block elements (interactive components)
        └── Composition objects (text, options)

Block Types Quick Reference

Type	Use For	Key Rules
`header`	Titles	150 chars max, `plain_text` only
`section`	Main content	3000 chars, can have accessory
`divider`	Visual separation	No content
`image`	Standalone images	HTTPS URL required, `alt_text` required
`context`	Metadata, timestamps	Max 10 elements, renders small/muted
`actions`	Button rows, menus	Max 25 elements
`table`	Tabular data	1 per message, max 100 rows, 20 columns
`rich_text`	Formatted text	Lists, quotes, code blocks, styled text

Table Block (NEW)

Constraints:

Only 1 table per message (error:
```
only_one_table_allowed
```
)
Table renders at BOTTOM of message (appended)
Max 100 rows, 20 columns
Cells can be
```
raw_text
```
or
```
rich_text
```

Basic Table

json

{
  "type": "table",
  "column_settings": [
    { "align": "left" },
    { "align": "center" },
    { "align": "right" }
  ],
  "rows": [
    [
      { "type": "raw_text", "text": "Name" },
      { "type": "raw_text", "text": "Count" },
      { "type": "raw_text", "text": "Value" }
    ],
    [
      { "type": "raw_text", "text": "Item A" },
      { "type": "raw_text", "text": "5" },
      { "type": "raw_text", "text": "$100" }
    ]
  ]
}

Column Settings

Property	Type	Description
`align`	string	`left` , `center` , or `right`
`is_wrapped`	boolean	Whether to wrap long text (default: false)

Table with Rich Text Cells (Links, Bold)

json

{
  "type": "table",
  "rows": [
    [
      { "type": "raw_text", "text": "Deal" },
      { "type": "raw_text", "text": "ARR" }
    ],
    [
      {
        "type": "rich_text",
        "elements": [
          {
            "type": "rich_text_section",
            "elements": [
              {
                "type": "link",
                "text": "Acme Corp",
                "url": "https://hubspot.com/deal/123"
              }
            ]
          }
        ]
      },
      {
        "type": "rich_text",
        "elements": [
          {
            "type": "rich_text_section",
            "elements": [
              { "type": "text", "text": "$50,000", "style": { "bold": true } }
            ]
          }
        ]
      }
    ]
  ]
}

Rich Text Block

Rich text provides more flexibility than mrkdwn. Use for complex formatting needs.

Rich Text Section (Basic)

json

{
  "type": "rich_text",
  "elements": [
    {
      "type": "rich_text_section",
      "elements": [
        { "type": "text", "text": "Hello " },
        { "type": "text", "text": "bold text", "style": { "bold": true } },
        { "type": "text", "text": " and " },
        { "type": "text", "text": "italic", "style": { "italic": true } }
      ]
    }
  ]
}

Rich Text List (Bullet/Numbered)

json

{
  "type": "rich_text",
  "elements": [
    {
      "type": "rich_text_section",
      "elements": [{ "type": "text", "text": "Features shipped:" }]
    },
    {
      "type": "rich_text_list",
      "style": "bullet",
      "elements": [
        {
          "type": "rich_text_section",
          "elements": [{ "type": "text", "text": "HubSpot integration" }]
        },
        {
          "type": "rich_text_section",
          "elements": [{ "type": "text", "text": "Mobile improvements" }]
        }
      ]
    }
  ]
}

Rich Text Quote

json

{
  "type": "rich_text",
  "elements": [
    {
      "type": "rich_text_quote",
      "elements": [
        {
          "type": "text",
          "text": "This is really going to change how we work."
        }
      ]
    }
  ]
}

Rich Text Element Types

Type	Properties	Use For
`text`	`text` , `style`	Plain/styled text
`link`	`url` , `text` , `style`	Clickable links
`user`	`user_id` , `style`	@mentions
`channel`	`channel_id` , `style`	#channel links
`usergroup`	`usergroup_id` , `style`	@group mentions
`emoji`	`name` , `unicode`	Emoji
`date`	`timestamp` , `format`	Formatted dates
`broadcast`	`range` (here/channel/everyone)	@here/@channel/@everyone

Text Style Object

json

{
  "style": {
    "bold": true,
    "italic": true,
    "strike": true,
    "code": true
  }
}

Block JSON Structures

Header Block

json

{
  "type": "header",
  "text": {
    "type": "plain_text",
    "text": ":rocket: Header Text Here",
    "emoji": true
  }
}

Section Block

json

{
  "type": "section",
  "text": {
    "type": "mrkdwn",
    "text": "*Bold* and _italic_ text with <https://example.com|links>"
  }
}

Section with Accessory (Button)

json

{
  "type": "section",
  "text": {
    "type": "mrkdwn",
    "text": "Your meeting has been processed."
  },
  "accessory": {
    "type": "button",
    "text": { "type": "plain_text", "text": "View", "emoji": true },
    "url": "https://app.askelephant.com/meetings/123",
    "action_id": "view_meeting"
  }
}

Section with Fields (Two-Column Layout)

json

{
  "type": "section",
  "fields": [
    { "type": "mrkdwn", "text": "*Status:*\nComplete" },
    { "type": "mrkdwn", "text": "*Duration:*\n45 min" },
    { "type": "mrkdwn", "text": "*Attendees:*\n4 people" },
    { "type": "mrkdwn", "text": "*Priority:*\nHigh" }
  ]
}

Rules: Max 10 fields, each max 2000 chars.

Divider Block

json

{
  "type": "divider"
}

Image Block

json

{
  "type": "image",
  "image_url": "https://example.com/chart.png",
  "alt_text": "Q4 revenue chart"
}

Context Block

json

{
  "type": "context",
  "elements": [
    {
      "type": "mrkdwn",
      "text": ":clock1: Posted at <!date^1706451200^{date_short_pretty} at {time}|Jan 28, 2026>"
    }
  ]
}

Actions Block

json

{
  "type": "actions",
  "block_id": "actions_1",
  "elements": [
    {
      "type": "button",
      "text": { "type": "plain_text", "text": "Approve", "emoji": true },
      "style": "primary",
      "action_id": "approve_btn",
      "value": "approved"
    },
    {
      "type": "button",
      "text": { "type": "plain_text", "text": "Reject", "emoji": true },
      "style": "danger",
      "action_id": "reject_btn",
      "value": "rejected"
    }
  ]
}

Button styles:

primary

(green),

danger

(red), or omit for default gray.

mrkdwn Syntax (NOT Standard Markdown!)

Text Formatting

Format	Syntax	Example
Bold	`text`	`important`
Italic	`_text_`	`_emphasis_`
Strikethrough	`~text~`	`~deleted~`
Code	`code`	`function()`
Code block	```code```	Multi-line
Quote	`>text`	Indented

Links and Mentions

Type	Syntax
URL	`<https://example.com>`
URL with text	`<https://example.com\|Click here>`
User mention	`<@U12345678>`
Channel link	`<#C12345678>`
@here	`<!here>`
@channel	`<!channel>`

Escape Characters

Character	Escape As
`&`	`&`
`<`	`<`
`>`	`>`

NOT Supported (Common Mistakes)

Wrong	Correct
`bold`	`bold`
`italic`	`_italic_`
`[text](url)`	`<url\|text>`
`# Header`	Use header block

Message Templates by Use Case

Newsletter Template (Polished)

Use for company-wide updates, weekly digests, or announcements.

json

{
  "text": "Paper Company Newsletter - November 12, 2019",
  "blocks": [
    {
      "type": "header",
      "text": {
        "type": "plain_text",
        "text": ":newspaper:  AskElephant Update  :newspaper:",
        "emoji": true
      }
    },
    {
      "type": "context",
      "elements": [
        {
          "text": "*January 28, 2026*  |  Product Team",
          "type": "mrkdwn"
        }
      ]
    },
    { "type": "divider" },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": ":loud_sound: *IN CASE YOU MISSED IT* :loud_sound:"
      }
    },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "The *HubSpot integration* shipped last week. Customers can now sync all their meeting data to HubSpot automatically."
      },
      "accessory": {
        "type": "button",
        "text": { "type": "plain_text", "text": "Learn More", "emoji": true },
        "url": "https://docs.askelephant.com/hubspot"
      }
    },
    { "type": "divider" },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": ":calendar: |   *UPCOMING*  | :calendar:"
      }
    },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "`02/01` *Speaker ID V2* — Improved speaker identification\n`02/15` *Admin Onboarding* — Streamlined workspace setup"
      }
    },
    { "type": "divider" },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "*FOR YOUR INFORMATION*"
      }
    },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": ":bulb: *Mobile app update* is now available. Make sure customers update for better recording reliability."
      }
    },
    { "type": "divider" },
    {
      "type": "context",
      "elements": [
        {
          "type": "mrkdwn",
          "text": ":pushpin: Questions? Drop them in *#product-forum*"
        }
      ]
    }
  ]
}

Rob Report (Revenue Team, Simple Language)

Use for CRO/revenue team updates with simplified language and customer-visible features only.

json

{
  "text": "What's New - January 27, 2026",
  "blocks": [
    {
      "type": "header",
      "text": {
        "type": "plain_text",
        "text": "What's New - January 27, 2026",
        "emoji": true
      }
    },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "Hey Revenue Team! Here's what shipped that you can use with customers right now."
      }
    },
    { "type": "divider" },
    {
      "type": "header",
      "text": {
        "type": "plain_text",
        "text": "What's New",
        "emoji": true
      }
    },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "*The app runs faster now* — Pages load quicker, especially with lots of conversations.\n\n*@ mentions work better in chat* — AskElephant understands who you're talking about more reliably."
      }
    },
    { "type": "divider" },
    {
      "type": "header",
      "text": {
        "type": "plain_text",
        "text": "What We Fixed",
        "emoji": true
      }
    },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "• Notification banners showing at wrong time\n• Scrolling no longer jumps around\n• Words getting cut off in meeting details"
      }
    },
    { "type": "divider" },
    {
      "type": "header",
      "text": {
        "type": "plain_text",
        "text": "Revenue Wins",
        "emoji": true
      }
    },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "*Total New ARR:* $20,399 (4 deals)\n*Expansion:* $5,700 (Hadco Construction)\n*Total ARR Impact:* $26,100"
      }
    },
    { "type": "divider" },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "_All features listed are available to your team now._"
      }
    },
    {
      "type": "table",
      "column_settings": [
        { "align": "left" },
        { "align": "center" },
        { "align": "center" },
        { "align": "center" },
        { "align": "center" }
      ],
      "rows": [
        [
          { "type": "raw_text", "text": "SDR" },
          { "type": "raw_text", "text": "Convos" },
          { "type": "raw_text", "text": "Pitches" },
          { "type": "raw_text", "text": "Meetings" },
          { "type": "raw_text", "text": "ICP Held" }
        ],
        [
          { "type": "raw_text", "text": "Jamis Benson" },
          { "type": "raw_text", "text": "7" },
          { "type": "raw_text", "text": "6" },
          { "type": "raw_text", "text": "4" },
          { "type": "raw_text", "text": "2" }
        ],
        [
          { "type": "raw_text", "text": "Carter Thomas" },
          { "type": "raw_text", "text": "8" },
          { "type": "raw_text", "text": "6" },
          { "type": "raw_text", "text": "5" },
          { "type": "raw_text", "text": "1" }
        ],
        [
          { "type": "raw_text", "text": "Team Total" },
          { "type": "raw_text", "text": "18" },
          { "type": "raw_text", "text": "14" },
          { "type": "raw_text", "text": "12" },
          { "type": "raw_text", "text": "3" }
        ]
      ]
    }
  ]
}

Daily Digest (Engineering/Product)

json

{
  "text": "AskElephant Daily Digest",
  "blocks": [
    {
      "type": "header",
      "text": {
        "type": "plain_text",
        "text": "AskElephant Daily Digest",
        "emoji": true
      }
    },
    {
      "type": "context",
      "elements": [
        { "type": "mrkdwn", "text": ":newspaper: Thursday, January 23, 2026" }
      ]
    },
    { "type": "divider" },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "*:trophy: Today's Headline*\n\n>*Dialpad Goes Live + Desktop Stability* — Another major telephony platform now integrated."
      }
    },
    { "type": "divider" },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "*:sparkles: New Features*\n\n*CRM Integrations*\n• Dialpad direct integration — full telephony support\n• Dialpad event handling — deduplication and routing\n\n*Recording & Capture*\n• Desktop MP4 audio — higher quality recordings\n• Web recording visual feedback"
      }
    },
    { "type": "divider" },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "*:wrench: Improvements*\n\n• Engagement page restored\n• AI description improvements\n• Query performance instrumented"
      }
    },
    { "type": "divider" },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "*:bug: Bugs Fixed: 6*\n\n• Auto logout toggle restored\n• Desktop recording stop reliability\n• Mobile push notification delivery"
      }
    },
    { "type": "divider" },
    {
      "type": "section",
      "text": { "type": "mrkdwn", "text": "*:busts_in_silhouette: Team Focus*" }
    },
    {
      "type": "section",
      "fields": [
        { "type": "mrkdwn", "text": "*Eduardo*\nDialpad, desktop, mobile" },
        { "type": "mrkdwn", "text": "*Matt Noxon*\nPerformance, dataloaders" },
        { "type": "mrkdwn", "text": "*Jason*\nStripe, PostHog, analytics" },
        { "type": "mrkdwn", "text": "*Dylan*\nVoiceprint, embeddings" }
      ]
    },
    { "type": "divider" },
    {
      "type": "context",
      "elements": [
        {
          "type": "mrkdwn",
          "text": ":chart_with_upwards_trend: *Stats:* 6 features | 3 improvements | 6 bugs fixed"
        },
        {
          "type": "mrkdwn",
          "text": ":rocket: *21 PRs merged* • *Eduardo leading with 10*"
        }
      ]
    }
  ]
}

Deal Closed Celebration

json

{
  "text": "Deal Closed: Acme Corp - $50,000 ARR",
  "blocks": [
    {
      "type": "header",
      "text": {
        "type": "plain_text",
        "text": ":tada: Deal Closed!",
        "emoji": true
      }
    },
    {
      "type": "section",
      "fields": [
        { "type": "mrkdwn", "text": "*Account:*\nAcme Corp" },
        { "type": "mrkdwn", "text": "*ARR:*\n$50,000" },
        { "type": "mrkdwn", "text": "*Rep:*\n<@U12345>" },
        { "type": "mrkdwn", "text": "*Type:*\nNew Business" }
      ]
    },
    {
      "type": "context",
      "elements": [
        {
          "type": "mrkdwn",
          "text": "Closed on <!date^1706451200^{date_long}|January 28, 2026>"
        }
      ]
    }
  ]
}

Approval Request (Interactive)

json

{
  "text": "Approval Needed: Enterprise Pricing",
  "blocks": [
    {
      "type": "header",
      "text": {
        "type": "plain_text",
        "text": ":raised_hand: Approval Needed",
        "emoji": true
      }
    },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "*Enterprise Pricing Proposal*\nNew tier at $2,500/mo for 50+ seats."
      }
    },
    {
      "type": "section",
      "fields": [
        { "type": "mrkdwn", "text": "*Requested by:*\n<@U12345>" },
        { "type": "mrkdwn", "text": "*Deadline:*\nFeb 1, 2026" }
      ]
    },
    {
      "type": "actions",
      "block_id": "approval_actions",
      "elements": [
        {
          "type": "button",
          "text": { "type": "plain_text", "text": "Approve", "emoji": true },
          "style": "primary",
          "action_id": "approve_proposal"
        },
        {
          "type": "button",
          "text": { "type": "plain_text", "text": "Reject", "emoji": true },
          "style": "danger",
          "action_id": "reject_proposal"
        },
        {
          "type": "button",
          "text": {
            "type": "plain_text",
            "text": "View Details",
            "emoji": true
          },
          "url": "https://notion.so/proposal-123",
          "action_id": "view_details"
        }
      ]
    }
  ]
}

Alert/Warning

json

{
  "text": "Alert: High API Error Rate",
  "blocks": [
    {
      "type": "header",
      "text": {
        "type": "plain_text",
        "text": ":rotating_light: Alert: High Error Rate",
        "emoji": true
      }
    },
    {
      "type": "section",
      "text": {
        "type": "mrkdwn",
        "text": "API error rate has exceeded 5% threshold.\n\n*Current rate:* 7.2%\n*Threshold:* 5%\n*Duration:* 15 minutes"
      }
    },
    {
      "type": "actions",
      "elements": [
        {
          "type": "button",
          "text": {
            "type": "plain_text",
            "text": "View Dashboard",
            "emoji": true
          },
          "url": "https://grafana.example.com/alerts",
          "style": "primary"
        },
        {
          "type": "button",
          "text": {
            "type": "plain_text",
            "text": "Acknowledge",
            "emoji": true
          },
          "action_id": "ack_alert"
        }
      ]
    },
    {
      "type": "context",
      "elements": [
        {
          "type": "mrkdwn",
          "text": ":clock1: Triggered at <!date^1706451200^{time}|2:30 PM>"
        }
      ]
    }
  ]
}

Template Selection Decision Tree

What are you sending?
│
├── Update for Revenue Team (Rob, AEs, SDRs)?
│   └── Use: Rob Report Template
│       • Simple language (high school reading level)
│       • Customer-visible features only
│       • Table block for SDR metrics
│
├── Company-wide announcement?
│   └── Use: Newsletter Template
│       • Header with emoji
│       • Context with date
│       • "In Case You Missed It" section
│       • "Upcoming" with dates in backticks
│       • "For Your Information" callout
│
├── Engineering/Product digest?
│   └── Use: Daily Digest Template
│       • Headline quote block
│       • Categorized sections (Features, Improvements, Bugs)
│       • Team Focus with fields
│       • Stats in context block
│
├── Deal closed?
│   └── Use: Deal Closed Template
│       • Header with :tada:
│       • Fields for Account/ARR/Rep/Type
│       • Context with date
│
├── Need approval?
│   └── Use: Approval Request Template
│       • Actions block with Approve/Reject buttons
│       • Fields for requester/deadline
│
├── Alert/Error?
│   └── Use: Alert Template
│       • :rotating_light: emoji
│       • Current vs threshold values
│       • Acknowledge button
│
└── Tabular data?
    └── Use: Table Block (1 per message)
        • Put at END of blocks array
        • Use column_settings for alignment
        • Center numeric columns

Block Selection Quick Guide

Content Type	Best Block
Title/Headline	`header`
Main text	`section`
Key-value pairs	`section` with `fields`
Text + button	`section` with `accessory`
Standalone image	`image`
Row of buttons	`actions`
Metadata/footer	`context`
Visual break	`divider`
Tabular data	`table` (1 per message, at end)
Complex formatting	`rich_text`

Validation Checklist

Before sending:

Valid JSON syntax
Fallback
```
text
```
field at root level
All
```
action_id
```
values unique
Character limits respected (header: 150, section: 3000)
Image URLs are HTTPS
mrkdwn syntax correct (not standard Markdown)
Max 50 blocks for messages
Only 1 table block (if using tables)
Table block is LAST in blocks array

Common Emoji Reference

Type	Emojis
Success	`:white_check_mark:` `:tada:` `:rocket:`
Alert	`:warning:` `:rotating_light:` `:exclamation:`
Info	`:information_source:` `:memo:` `:newspaper:`
Revenue	`:moneybag:` `:chart_with_upwards_trend:` `:trophy:`
Meetings	`:movie_camera:` `:calendar:` `:busts_in_silhouette:`
Dev	`:hammer_and_wrench:` `:gear:` `:package:` `:bug:`
Time	`:clock1:` `:hourglass:` `:stopwatch:`
Category	`:sparkles:` `:wrench:` `:loud_sound:` `:bulb:`

Date Formatting

Use

<!date^TIMESTAMP^FORMAT|FALLBACK>

in mrkdwn.

Token	Output
`{date_num}`	2026-01-28
`{date_short}`	Jan 28, 2026
`{date_long}`	Monday, January 28th, 2026
`{date_pretty}`	today/yesterday/tomorrow or date
`{time}`	2:34 PM
`{ago}`	3 minutes ago

Example:

<!date^1706451200^{date_short_pretty} at {time}|Jan 28, 2026>

Testing

Recommend testing in Block Kit Builder before sending.

slack-block-kit

NPX Install

Tags

SKILL.md Content

Slack Block Kit Formatting Skill

When to Apply This Skill

MCP Tools

Architecture

Block Types Quick Reference

Table Block (NEW)

Basic Table

Column Settings

Table with Rich Text Cells (Links, Bold)

Rich Text Block

Rich Text Section (Basic)

Rich Text List (Bullet/Numbered)

Rich Text Quote

Rich Text Element Types

Text Style Object

Block JSON Structures

Header Block

Section Block

Section with Accessory (Button)

Section with Fields (Two-Column Layout)

Divider Block

Image Block

Context Block

Actions Block

mrkdwn Syntax (NOT Standard Markdown!)

Text Formatting

Links and Mentions

Escape Characters

NOT Supported (Common Mistakes)

Message Templates by Use Case

Newsletter Template (Polished)

Rob Report (Revenue Team, Simple Language)

Daily Digest (Engineering/Product)

Deal Closed Celebration

Approval Request (Interactive)

Alert/Warning

Template Selection Decision Tree

Block Selection Quick Guide

Validation Checklist

Common Emoji Reference

Date Formatting

Testing