Slack Block

The Slack block provides comprehensive access to Slack messaging, channels, modals, and interactive components within your workflows.

Overview

Use the Slack block when you need to:

Send notifications to channels or users
Create approval workflows with interactive buttons
Build rich messages with Block Kit
Manage channels and users programmatically
Upload files and add reactions

Prerequisites

Slack Connection: Configure OAuth via Nango with slack provider
Bot Permissions: Bot must be added to target channels
Scopes Required: Varies by action (see action-specific requirements)

Configuration

Step Definition

{
  "id": "notify-team",
  "type": "slack",
  "name": "Send Team Notification",
  "config": {
    "action": "sendMessage",
    "channel": "#billing",
    "text": "Invoice {{input.invoice_number}} has been paid!"
  }
}

Configuration Fields

Field	Type	Required	Description
`action`	string	Yes	The Slack action to execute
`channel`	string	Varies	Channel ID or name (e.g., `#general`, `C1234567890`)
`text`	string	Varies	Message text (supports mrkdwn)
`blocks`	array	Varies	Block Kit blocks for rich layouts
`user`	string	Varies	User ID for user-specific actions

Available Actions

Message Actions

sendMessage

Send a message to a channel or DM.

Required Scopes: chat:write, chat:write.public (for non-member channels)

{
  "id": "send-notification",
  "type": "slack",
  "config": {
    "action": "sendMessage",
    "channel": "#sales",
    "text": "New deal closed: {{input.deal_name}} for ${{input.amount}}",
    "threadTs": "{{input.parent_message_ts}}",
    "unfurlLinks": false,
    "mrkdwn": true
  }
}

Parameters:

Field	Type	Description
`channel`	string	Channel ID or name
`text`	string	Message text (required if no blocks)
`blocks`	array	Block Kit blocks
`threadTs`	string	Reply to thread
`replyBroadcast`	boolean	Also post to channel when replying
`unfurlLinks`	boolean	Enable link previews
`unfurlMedia`	boolean	Enable media previews
`mrkdwn`	boolean	Enable mrkdwn formatting (default: true)
`attachments`	array	Legacy attachments
`metadata`	object	Message metadata

Output:

{
  "ok": true,
  "channel": "C1234567890",
  "ts": "1234567890.123456",
  "message": {
    "text": "New deal closed...",
    "user": "U1234567890",
    "ts": "1234567890.123456"
  }
}

sendEphemeral

Send an ephemeral message (only visible to one user).

Required Scopes: chat:write

{
  "id": "private-hint",
  "type": "slack",
  "config": {
    "action": "sendEphemeral",
    "channel": "#general",
    "user": "{{input.user_id}}",
    "text": "Only you can see this message!"
  }
}

Parameters:

Field	Type	Description
`channel`	string	Channel ID
`user`	string	User ID to show message to
`text`	string	Message text
`blocks`	array	Block Kit blocks
`threadTs`	string	Thread timestamp

scheduleMessage

Schedule a message to be sent later.

Required Scopes: chat:write

{
  "id": "schedule-reminder",
  "type": "slack",
  "config": {
    "action": "scheduleMessage",
    "channel": "#reminders",
    "text": "Don't forget: {{input.reminder_text}}",
    "postAt": "{{input.reminder_time}}"
  }
}

Parameters:

Field	Type	Description
`channel`	string	Channel ID
`postAt`	number/string	Unix timestamp or ISO 8601 datetime
`text`	string	Message text
`blocks`	array	Block Kit blocks

Output:

{
  "ok": true,
  "channel": "C1234567890",
  "scheduled_message_id": "Q1234567890",
  "post_at": 1234567890
}

updateMessage

Update an existing message.

Required Scopes: chat:write

{
  "id": "update-status",
  "type": "slack",
  "config": {
    "action": "updateMessage",
    "channel": "{{steps.send-message.output.channel}}",
    "ts": "{{steps.send-message.output.ts}}",
    "text": "Status: Completed!"
  }
}

Parameters:

Field	Type	Description
`channel`	string	Channel ID
`ts`	string	Message timestamp to update
`text`	string	New message text
`blocks`	array	New Block Kit blocks

deleteMessage

Delete a message.

Required Scopes: chat:write

{
  "id": "cleanup-message",
  "type": "slack",
  "config": {
    "action": "deleteMessage",
    "channel": "{{input.channel_id}}",
    "ts": "{{input.message_ts}}"
  }
}

getPermalink

Get a permanent link to a message.

{
  "id": "get-link",
  "type": "slack",
  "config": {
    "action": "getPermalink",
    "channel": "{{input.channel_id}}",
    "messageTs": "{{input.message_ts}}"
  }
}

Output:

{
  "ok": true,
  "channel": "C1234567890",
  "permalink": "https://workspace.slack.com/archives/C1234567890/p1234567890123456"
}

Reaction Actions

addReaction

Add an emoji reaction to a message.

Required Scopes: reactions:write

{
  "id": "react-to-message",
  "type": "slack",
  "config": {
    "action": "addReaction",
    "channel": "{{input.channel_id}}",
    "timestamp": "{{input.message_ts}}",
    "name": "white_check_mark"
  }
}

Parameters:

Field	Type	Description
`channel`	string	Channel ID
`timestamp`	string	Message timestamp
`name`	string	Emoji name (without colons)

removeReaction

Remove an emoji reaction.

{
  "id": "remove-reaction",
  "type": "slack",
  "config": {
    "action": "removeReaction",
    "channel": "{{input.channel_id}}",
    "timestamp": "{{input.message_ts}}",
    "name": "eyes"
  }
}

File Actions

uploadFile

Upload a file to Slack.

Required Scopes: files:write

{
  "id": "upload-report",
  "type": "slack",
  "config": {
    "action": "uploadFile",
    "channels": ["#reports", "#finance"],
    "content": "{{input.csv_content}}",
    "filename": "report-{{input.date}}.csv",
    "title": "Monthly Report",
    "initialComment": "Here's the monthly report!"
  }
}

Parameters:

Field	Type	Description
`channels`	string/array	Channel(s) to share file
`content`	string	Text content for the file
`file`	string	Base64 encoded file content
`filename`	string	Name of the file
`filetype`	string	File type (e.g., `csv`, `pdf`)
`title`	string	Title of the file
`initialComment`	string	Comment to add with file
`threadTs`	string	Thread to upload to

getFile

Get file information.

{
  "id": "get-file-info",
  "type": "slack",
  "config": {
    "action": "getFile",
    "fileId": "{{input.file_id}}"
  }
}

deleteFile

Delete a file.

{
  "id": "delete-file",
  "type": "slack",
  "config": {
    "action": "deleteFile",
    "fileId": "{{input.file_id}}"
  }
}

Modal/View Actions

openModal

Open a modal view (requires trigger_id from interactive event).

Required Scopes: None (uses bot token)

{
  "id": "open-approval-modal",
  "type": "slack",
  "config": {
    "action": "openModal",
    "triggerId": "{{input.trigger_id}}",
    "view": {
      "type": "modal",
      "title": { "type": "plain_text", "text": "Approve Request" },
      "submit": { "type": "plain_text", "text": "Approve" },
      "close": { "type": "plain_text", "text": "Cancel" },
      "blocks": [
        {
          "type": "section",
          "text": {
            "type": "mrkdwn",
            "text": "Approve invoice #{{input.invoice_number}}?"
          }
        },
        {
          "type": "input",
          "block_id": "notes_block",
          "element": {
            "type": "plain_text_input",
            "action_id": "notes_input",
            "multiline": true,
            "placeholder": { "type": "plain_text", "text": "Add notes..." }
          },
          "label": { "type": "plain_text", "text": "Notes" }
        }
      ]
    }
  }
}

Parameters:

Field	Type	Description
`triggerId`	string	Trigger ID from interactive event
`view`	object	Modal view definition

updateModal

Update an existing modal.

{
  "id": "update-modal",
  "type": "slack",
  "config": {
    "action": "updateModal",
    "viewId": "{{input.view_id}}",
    "view": {
      "type": "modal",
      "title": { "type": "plain_text", "text": "Updated Modal" },
      "blocks": [...]
    }
  }
}

Parameters:

Field	Type	Description
`viewId`	string	View ID to update
`externalId`	string	Alternative: external ID
`view`	object	Updated view definition
`hash`	string	Optional hash for conflict detection

pushModal

Push a new view onto the modal stack.

{
  "id": "push-details",
  "type": "slack",
  "config": {
    "action": "pushModal",
    "triggerId": "{{input.trigger_id}}",
    "view": {
      "type": "modal",
      "title": { "type": "plain_text", "text": "Details" },
      "blocks": [...]
    }
  }
}

publishHomeTab

Publish content to a user's Home tab.

Required Scopes: None (uses bot token)

{
  "id": "update-home",
  "type": "slack",
  "config": {
    "action": "publishHomeTab",
    "userId": "{{input.user_id}}",
    "view": {
      "type": "home",
      "blocks": [
        {
          "type": "section",
          "text": {
            "type": "mrkdwn",
            "text": "Welcome, *{{input.user_name}}*!"
          }
        },
        {
          "type": "section",
          "text": {
            "type": "mrkdwn",
            "text": "You have {{input.pending_count}} pending approvals."
          }
        }
      ]
    }
  }
}

getUser

Get user information.

Required Scopes: users:read

{
  "id": "get-user",
  "type": "slack",
  "config": {
    "action": "getUser",
    "userId": "{{input.user_id}}",
    "includeLocale": true
  }
}

Output:

{
  "ok": true,
  "user": {
    "id": "U1234567890",
    "name": "johndoe",
    "real_name": "John Doe",
    "profile": {
      "email": "john@example.com",
      "display_name": "John"
    }
  }
}

listUsers

List workspace users.

Required Scopes: users:read

{
  "id": "list-users",
  "type": "slack",
  "config": {
    "action": "listUsers",
    "limit": 100,
    "includeLocale": false
  }
}

lookupUserByEmail

Find a user by email address.

Required Scopes: users:read.email

{
  "id": "find-user",
  "type": "slack",
  "config": {
    "action": "lookupUserByEmail",
    "email": "{{input.email}}"
  }
}

Channel Actions

getChannel

Get channel information.

Required Scopes: channels:read, groups:read

{
  "id": "get-channel",
  "type": "slack",
  "config": {
    "action": "getChannel",
    "channelId": "{{input.channel_id}}",
    "includeNumMembers": true
  }
}

listChannels

List channels.

Required Scopes: channels:read, groups:read

{
  "id": "list-channels",
  "type": "slack",
  "config": {
    "action": "listChannels",
    "types": "public_channel,private_channel",
    "excludeArchived": true,
    "limit": 100
  }
}

Parameters:

Field	Type	Description
`types`	string	Channel types (public_channel, private_channel, mpim, im)
`excludeArchived`	boolean	Exclude archived channels (default: true)
`limit`	number	Max results (default: 100)
`cursor`	string	Pagination cursor

createChannel

Create a new channel.

Required Scopes: channels:manage, groups:write

{
  "id": "create-project-channel",
  "type": "slack",
  "config": {
    "action": "createChannel",
    "name": "proj-{{input.project_slug}}",
    "isPrivate": false
  }
}

inviteToChannel

Invite users to a channel.

Required Scopes: channels:manage, groups:write

{
  "id": "invite-team",
  "type": "slack",
  "config": {
    "action": "inviteToChannel",
    "channelId": "{{steps.create-channel.output.channel.id}}",
    "users": ["U111111", "U222222", "U333333"]
  }
}

archiveChannel

Archive a channel.

{
  "id": "archive-channel",
  "type": "slack",
  "config": {
    "action": "archiveChannel",
    "channelId": "{{input.channel_id}}"
  }
}

setChannelTopic

Set channel topic.

{
  "id": "set-topic",
  "type": "slack",
  "config": {
    "action": "setChannelTopic",
    "channelId": "{{input.channel_id}}",
    "topic": "Project: {{input.project_name}} | Status: {{input.status}}"
  }
}

getChannelHistory

Get channel message history.

Required Scopes: channels:history, groups:history

{
  "id": "get-history",
  "type": "slack",
  "config": {
    "action": "getChannelHistory",
    "channelId": "{{input.channel_id}}",
    "limit": 50,
    "oldest": "{{input.since_timestamp}}"
  }
}

Bookmark Actions

addBookmark

Add a bookmark to a channel.

Required Scopes: bookmarks:write

{
  "id": "add-bookmark",
  "type": "slack",
  "config": {
    "action": "addBookmark",
    "channelId": "{{input.channel_id}}",
    "title": "Project Dashboard",
    "type": "link",
    "link": "https://dashboard.example.com/{{input.project_id}}"
  }
}

Block Kit Examples

Rich Notification with Buttons

{
  "id": "approval-request",
  "type": "slack",
  "config": {
    "action": "sendMessage",
    "channel": "#approvals",
    "text": "New approval request",
    "blocks": [
      {
        "type": "header",
        "text": { "type": "plain_text", "text": "Invoice Approval Required" }
      },
      {
        "type": "section",
        "fields": [
          { "type": "mrkdwn", "text": "*Invoice:*\n#{{input.invoice_number}}" },
          { "type": "mrkdwn", "text": "*Amount:*\n${{input.amount}}" },
          { "type": "mrkdwn", "text": "*Vendor:*\n{{input.vendor_name}}" },
          { "type": "mrkdwn", "text": "*Due Date:*\n{{input.due_date}}" }
        ]
      },
      {
        "type": "actions",
        "block_id": "approval_actions",
        "elements": [
          {
            "type": "button",
            "text": { "type": "plain_text", "text": "Approve" },
            "action_id": "approve_invoice",
            "style": "primary",
            "value": "{{input.invoice_id}}"
          },
          {
            "type": "button",
            "text": { "type": "plain_text", "text": "Reject" },
            "action_id": "reject_invoice",
            "style": "danger",
            "value": "{{input.invoice_id}}"
          },
          {
            "type": "button",
            "text": { "type": "plain_text", "text": "View Details" },
            "action_id": "view_invoice",
            "url": "https://app.example.com/invoices/{{input.invoice_id}}"
          }
        ]
      }
    ]
  }
}

Status Update with Context

{
  "id": "pipeline-status",
  "type": "slack",
  "config": {
    "action": "sendMessage",
    "channel": "#deployments",
    "blocks": [
      {
        "type": "section",
        "text": {
          "type": "mrkdwn",
          "text": "{{#if input.success}}:white_check_mark:{{else}}:x:{{/if}} *Build {{input.build_number}}* {{input.status}}"
        }
      },
      {
        "type": "context",
        "elements": [
          { "type": "mrkdwn", "text": "Branch: `{{input.branch}}`" },
          { "type": "mrkdwn", "text": "Commit: `{{input.commit_sha}}`" },
          { "type": "mrkdwn", "text": "Duration: {{input.duration}}s" }
        ]
      }
    ]
  }
}

Template Variables

Access workflow data in your Slack configuration:

Variable	Description
`{{input.field}}`	Workflow trigger input
`{{steps.stepId.output.field}}`	Previous step output
`{{variables.name}}`	Workflow variables
`{{env.VAR}}`	Environment variables

Error Handling

Common Errors

Error	Cause	Solution
`channel_not_found`	Invalid channel ID/name	Verify channel exists and bot has access
`not_in_channel`	Bot not in channel	Invite bot to channel or use `chat:write.public`
`invalid_blocks`	Malformed Block Kit	Validate blocks with Block Kit Builder
`trigger_expired`	Stale trigger_id	Trigger IDs expire in 3 seconds
`missing_scope`	Insufficient permissions	Add required OAuth scopes
`rate_limited`	Too many requests	Implement backoff, respect retry-after

Error Response

{
  "ok": false,
  "error": "channel_not_found",
  "response_metadata": {
    "messages": ["Channel not found or bot not a member"]
  }
}

Rate Limits

Tier	Limit	Description
Tier 1	1/min	Low-frequency methods
Tier 2	20/min	Most methods
Tier 3	50/min	High-frequency methods
Tier 4	100/min	Very high-frequency
Special	Varies	chat.postMessage: ~1/sec per channel

Slack returns 429 Too Many Requests with Retry-After header when limits are exceeded.

Email Block - Send email notifications
Action Steps - Other integration actions
Condition Steps - Conditional logic

Example Workflow

Complete approval workflow with Slack:

{
  "name": "Invoice Approval Workflow",
  "trigger": {
    "type": "webhook",
    "provider": "quickbooks",
    "events": ["invoice.created"]
  },
  "steps": [
    {
      "id": "check-amount",
      "type": "condition",
      "config": {
        "conditions": {
          "left": "{{input.payload.TotalAmt}}",
          "operator": "gt",
          "right": 1000
        },
        "then": ["request-approval"],
        "else": ["auto-approve"]
      }
    },
    {
      "id": "request-approval",
      "type": "slack",
      "config": {
        "action": "sendMessage",
        "channel": "#finance-approvals",
        "text": "Invoice requires approval",
        "blocks": [
          {
            "type": "section",
            "text": {
              "type": "mrkdwn",
              "text": "*New Invoice Requires Approval*\n\nAmount: ${{input.payload.TotalAmt}}\nVendor: {{input.payload.CustomerRef.name}}"
            }
          },
          {
            "type": "actions",
            "elements": [
              {
                "type": "button",
                "text": { "type": "plain_text", "text": "Approve" },
                "action_id": "approve_{{input.payload.Id}}",
                "style": "primary"
              },
              {
                "type": "button",
                "text": { "type": "plain_text", "text": "Reject" },
                "action_id": "reject_{{input.payload.Id}}",
                "style": "danger"
              }
            ]
          }
        ]
      }
    },
    {
      "id": "auto-approve",
      "type": "slack",
      "config": {
        "action": "sendMessage",
        "channel": "#finance-log",
        "text": ":white_check_mark: Auto-approved invoice #{{input.payload.DocNumber}} for ${{input.payload.TotalAmt}}"
      }
    }
  ]
}

Slack Block

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