Rich Messages

Buttons, cards, and effects across Discord, Telegram, Slack, and more

Can my agent send buttons people can click? A poll? A pretty card with an image? On the platforms that support those, yes — your agent describes them once in a platform-neutral way and Comis renders them natively per-channel. On platforms that do not (IRC, Email, Signal, iMessage), Comis falls back to plain text so the message still gets through.

Your agents can send more than just text. Rich messages include interactive buttons, styled cards with images and fields, and special effects like spoiler text. Comis provides a unified way to create these — your agent writes them once, and Comis renders them correctly on each platform using that platform’s native features.

Polls are also available, but they are dispatched through the platform_action tool (action: poll) rather than as part of a normal message send. See Platform Actions for the full poll parameters.

You don’t need to understand the technical details to use this feature. The configuration examples below are copy-paste ready.

What Your Agent Can Send

Comis supports three types of rich messages plus polls via platform actions:

• Buttons — Clickable actions that appear below a message. Users tap a button instead of typing a response. Great for choices like “Yes/No,” “Approve/Reject,” or navigation menus.

• Cards (Embeds) — Styled message blocks with a title, description, optional image, color accent, and structured fields. Think of them like a mini web page embedded in the chat.

• Effects — Special delivery modifiers like spoiler (content hidden until tapped) and silent (no notification sound).

• Polls — Question + 2-10 options, dispatched via platform_action (not the message tool). Available on Discord, Telegram, and WhatsApp.

Platform Support

Not every platform supports every rich message type. The table below shows what works where.

Feature	Discord	Telegram	Slack	LINE	WhatsApp	Signal	iMessage	IRC	Email
Buttons	Yes	Yes	Yes	No	Stubbed (text only)	No	No	No	No
Cards/Embeds	Yes	Styled text	Yes	No	No	No	No	No	No
Spoiler	Yes	Yes	No	No	No	No	No	No	No
Silent	Yes	Yes	No	No	No	No	No	No	No
Polls (via platform_action)	Yes	Yes	No	No	Yes	No	No	No	No

When your agent tries to send a rich message to a platform that does not support it, Comis gracefully falls back to plain text. Buttons become a numbered list, cards become formatted text, and polls are not sent. Your agent’s message always gets through.

Buttons

Buttons give users a quick way to respond without typing. Your agent defines the button labels and what happens when each is clicked. Buttons are the most commonly used rich message type — they work on the most platforms and provide a simple, intuitive interaction.

Button Types

There are two kinds of buttons:

• Action buttons use callback_data — when a user clicks the button, the identifier is sent back to the agent so it knows which button was pressed.
• Link buttons use url — clicking the button opens a web page in the user’s browser. No data is sent back to the agent.

Button Properties

Property	Type	Description
text	string	The label shown on the button
callback_data	string	Identifier sent back when the button is clicked
url	string	URL to open (for link buttons — mutually exclusive with callback_data)
style	string	Visual hint: primary, secondary, danger, or link

Each button is either an action button (sends callback_data back to the agent when clicked) or a link button (opens a URL in the user’s browser). You cannot have both callback_data and url on the same button.

Platform Limits

Discord

Buttons appear in “action rows.” Maximum 5 buttons per row and 5 rows per message (25 buttons total). Supports all 4 styles: primary (blue), secondary (gray), danger (red), and link (opens a URL).

Telegram

Buttons appear as inline keyboards below the message. Maximum callback_data length is 64 bytes — longer values are silently truncated. URL buttons and callback buttons are both supported. Styles are not visually distinct (Telegram shows all buttons the same way regardless of the style property).

Slack

Buttons appear in actions blocks. Only primary and danger styles are supported — other styles fall back to the default appearance. Each button needs a unique identifier internally.

LINE

The LINE adapter ships a Flex Message builder (flex-builder.ts) for rich-menu actions, but its sendMessage path does not currently render RichButton rows — buttons are not delivered when sent through the message tool. The plugin self-declares buttons: false. The Flex builder limits action labels to 20 characters and postback data to 300 characters when used directly through internal APIs.

WhatsApp

The WhatsApp plugin self-declares buttons: true, but the current adapter implementation logs button payloads and falls back to plain text — the buttons themselves are not yet rendered to the WhatsApp Business API. Treat WhatsApp button support as not yet implemented for end users.

Keep callback_data short (under 64 bytes) and button labels under 20 characters for maximum cross-platform compatibility.

Cards and Embeds

Cards are styled message blocks that stand out from regular text. They can include a title, description, image, color accent, and structured fields. Cards are the most visually rich message type and are ideal for displaying structured information like status reports, product listings, or summaries.

Card Properties

Property	Type	Description
title	string	Card title (bold, larger text)
description	string	Card body text
image_url	string	URL for a thumbnail or hero image
color	number	Accent color as integer (e.g., 0x0099FF for blue)
fields	array	Structured key-value pairs with name, value, and inline flag
buttons	array	Button rows attached to the card

Fields are key-value pairs that appear inside the card. Each field has a name (the label), a value (the content), and an inline flag. When inline is true, fields are displayed side by side rather than stacked vertically.

How Cards Render on Each Platform

Discord

Full embed support. Supports title, description, color sidebar, up to 25 fields (inline or stacked), thumbnail image, and footer. Discord provides the richest card experience with native embed styling, color accents, and image previews.

Telegram

No native embed format. Cards are rendered as HTML-formatted text with bold titles, italic descriptions, and an invisible link for image previews. The result is functional but less visually striking than Discord embeds.

Slack

Uses Block Kit section blocks. Title becomes a header block, description becomes markdown text, fields render as two-column sections, and images become accessory elements. Slack’s block layout provides a clean, structured appearance.

LINE

The LINE adapter does not render RichCard from the message tool today — the plugin self-declares cards: false. Cards sent to LINE fall back to the plain-text equivalent.

Polls (via platform_action)

Polls let your agent ask a question and collect votes. Users click to select their answer, and results are visible to everyone in the chat.

Polls are dispatched through the platform_action tool with action: "poll", not as part of a normal message send. See Platform Actions for the full tool reference.

Poll Input Properties

Property	Type	Description
question	string	The poll question (required, non-empty)
options	array	2 to 10 answer choices
maxSelections	number	Maximum selections per voter (default: 1, must not exceed number of options)
durationHours	number	How long the poll stays open. Clamped to 1-168 hours; defaults to 24 hours when omitted.

The maxSelections property controls whether users can pick one answer or multiple answers. Set it to 1 for single-choice polls (like “Which day works best?”) or higher for multi-select polls (like “Which features do you want?”).

Platform Support

Discord

Native poll support via platform_action (action: “poll”). Duration is clamped to 1-168 hours (1 hour to 7 days). Polls appear as a dedicated message type with clickable options and a live vote count.

Telegram

Native poll support via platform_action. Polls appear below the chat message with radio buttons (single-select) or checkboxes (multi-select). Results update in real time as users vote.

WhatsApp

Polls are sent through the WhatsApp adapter’s platform_action handler using Baileys’ poll-message support. Vote-result normalization is not yet wired (see code TODO), so the agent receives the poll-creation confirmation but does not yet receive vote callbacks.

Other platforms

Polls are not supported on Slack, LINE, Signal, iMessage, IRC, or Email. Calling platform_action with action: "poll" on these platforms returns an error. The accompanying text message (if any) is still sent through the normal message path.

Effects

Effects are delivery modifiers that change how a message appears or is delivered. They do not change the message content itself. Effects can be combined with any other rich message type — for example, you can send a card with a spoiler effect.

Spoiler

Content is hidden behind a spoiler tag. Users must tap or click to reveal it. Supported on Discord (spoiler markdown formatting) and Telegram (spoiler entity).

Common uses:

• Hiding quiz answers until the user is ready
• Concealing plot spoilers in entertainment channels
• Masking sensitive information that should not be visible at a glance

Silent

The message is delivered without triggering a notification sound. Supported on Discord (silent message flag) and Telegram (notification disabled).

Common uses:

• Low-priority status updates or periodic reports
• Automated messages that should not interrupt the user
• Batch notifications where only the first should make a sound

Effects are ignored on platforms that do not support them. The message is still delivered normally — it just does not have the spoiler or silent behavior.

How Agents Create Rich Messages

Agents create rich messages through the message tool. The agent specifies buttons, cards, polls, or effects as part of the message action. For example, an agent might send a card with a summary and a row of buttons for the user to choose from.

The agent does not need to know the specifics of each platform’s message format. Comis handles the conversion automatically. A single rich message definition works across all connected platforms, with Comis adapting it to each platform’s native capabilities.

For the full tool reference and usage examples, see Messaging Tools.

Your agent does not need to know which platform the user is on. Comis automatically adapts the rich message format. The agent writes one message, and it renders correctly everywhere it is supported.

Fallback Behavior

When a rich message is sent to a platform that does not support it, Comis converts it to the closest plain text equivalent:

Rich Type	Fallback
Buttons	Plain text only (button rows are dropped on unsupported platforms)
Cards	Plain text only (cards are dropped on unsupported platforms)
Spoiler	Content shown without hiding
Silent	Normal notification behavior
Polls (via platform_action)	Action returns an error on unsupported platforms; no fallback message is generated

This means your agent can always use rich messages without worrying about platform compatibility. Users on platforms with full support get the native interactive experience, while users on simpler platforms still receive the essential information as plain text.

Fallback conversion is automatic. You do not need to define separate message formats for different platforms. Comis detects the target platform and chooses the best rendering approach available.

Related

Messaging Tools

message tool reference with rich message examples

Channels Overview

Platform-specific capabilities and limits

Media Overview

Back to media overview

Platform Actions

Platform-specific moderation tools