Block kit in Workbot for Slack

Block Kit (opens new window) is Slack's UI framework, which offers users more control and flexibility when building messages for Slack.

You can stack the "blocks" and customize the order and appearance of each block, as well as the elements within each block. The table below shows the different types of blocks and the actions that support them.

Blocks can be used in the following Slack surfaces:

Surface	Applicable actions
Messages	Post message, Post command reply
Modals	Open/update or push modal
App home	Publish app home view

Compatibility with message attachments

Post message and post command reply previously used message attachments to construct messages. Blocks can be used together with message attachments.

You can optionally provide secondary attachments, which will display below any defined blocks.

Behavior of blocks when used with message attachments

• When both blocks and message attachments are defined, blocks will always appear above message attachments.

• When any blocks are defined, any input in the Message text field will be used as the Slack notification message.

Supported blocks

Supported blocks are displayed in the table below.

Blocks	Description
Section with text	Displays text.
Section with image	Displays text alongside an image thumbnail.
Section with button	Displays text alongside a button. You can configure Workato to take one of the following actions on button-click: continue recipe, run a bot command, or open a URL.
Section with fields	Displays text, along with an array of title-value fields, rendered in 2 columns beneath the section text. Maximum number of fields is 10. Maximum length for the text in each field is 2000 characters.
Section with select menu	Displays text, alongside a select menu. Supports Slack's built-in dynamic menus such as Select user, Select conversation, Select channel. You can also define your own custom dynamic menu. On submission, a menu option invokes another recipe and passes on any command input values it has.
Section with overflow menu	Displays text, alongside an overflow menu. Supports static or dynamically generated overflow menu options. On submission, an overflow menu option invokes another recipe and passes on any command input values it has.
Section with date picker	Displays text, alongside a date picker. On date selection, a date picker invokes another recipe and passes on the selected date via a date parameter. You can customize the name of this date parameter. You can optionally pass additional command input values together with the date parameter.
Repeat block group	This a special block type that's available only on the Workato bot platform. The repeat block group allows you to define a set of blocks to use as a pattern. By iterating through an existing list and mapping the list fields to the fields of the blocks in the pattern, you can dynamically generate repeat blocks.
Divider	A content divider, like an <hr>, used to split up different blocks inside of a message.
Image	Displays an image using a provided public URL.
Actions	A block that can hold multiple interactive elements like buttons, overflow menus, select menus, and date pickers.
Context	Displays message context, which can include both images and texts. All images and texts will be joined together into a single string, in the order they appear in.

Limitations

Max no. of blocks

The following table shows the max number of blocks that Slack allows you to publish on a surface.

Surface	Max no. of blocks
Messages	50
Modals	100
App home	100

Character Limits in Block kit elements

When posting to surfaces on Slack, Workbot uses the value & action_id fields to pass bot commands and parameters. These fields have character limits. While bot commands & command input values are exposed to the user for use, Workbot reserves 9 characters for internal use. Additionally, spaces also contribute to the character count.

WARNING

Since Submit button/menu option commands, Command input values, spaces & 9 characters (Workbot internal use) are combined and passed through value or action_id, they share the same character limit.

The following table shows the character limits found in block kit elements.

Block kit elements	Character count contributors	Character limit	Field used in payload	Surfaces
Section with button Actions: Button	Submit button command Command input values Workbot internal use (9 characters) Spaces	2000	value	Messages App home Modals
Section with select menu	Submit menu option command Command input values Workbot internal use (9 characters) Spaces	255	action_id	Messages App home Modals
Actions: select menu	Submit menu option command Command input values Workbot internal use (9 characters) Spaces	75	value	Messages App home Modals
Section with overflow menu Actions: Overflow menu	Submit menu option command Command input values Workbot internal use (9 characters) Spaces	75	value	Messages App home Modals
Section with date picker Actions: Date picker	Submit menu option command Command input values Workbot internal use (9 characters) Spaces	255	action_id	Messages App home Modals
Select menu input *Types: Custom, Dynamic*	Value to pass when this option is selected	75	value	Modals only
Section with radio buttons	Submit menu option command Command input values Workbot internal use (9 characters) Spaces	75	value	Modals only
Checkboxes input	Value	75	value	Modals only
Radio buttons input	Value	75	value	Modals only