RCS rich card limits
Google's RCS Business Messaging (RBM) API reference sets the limits a rich card must respect. Messages that break them are rejected by the API, so this builder checks them as you type.
Source: Google, RBM reference for phones.agentMessages, https://developers.google.com/business-communications/rcs-business-messaging/reference/rest/v1/phones.agentMessages, and the send messages guide, https://developers.google.com/business-communications/rcs-business-messaging/guides/build/messages/send (checked October 2026).
- Card title: up to 200 characters. Description: up to 2,000 characters.
- Suggestions on a card: up to 4 replies or actions, each up to 25 characters.
- Suggestion chips under the message: up to 11.
- Carousel: 2 to 10 cards, with card width SMALL (120 DP) or MEDIUM (232 DP).
- Media height: SHORT (112 DP), MEDIUM (168 DP) or TALL (264 DP). Media files up to 100 MB; thumbnails up to 100 kB.
- Postback data and fallback URLs: up to 2,048 characters. Plain text messages: up to 3,072 characters.
Standalone card or carousel?
Use a standalone card when there is one thing to act on: a booking to confirm, a parcel to track, a payment to complete. A vertical card puts media on top and works best with a strong image. A horizontal card places a thumbnail beside the text, which suits receipts and status updates; it needs a title, description or suggestion alongside its media.
Use a carousel when the customer is choosing: products, flights, plans, appointment slots. Keep cards consistent, all with media or all without, and give titles and descriptions a similar length, since carousel cards are shown at a uniform height. Put the most likely choice first.
Suggested replies and actions
Suggested replies send a fixed text back to your agent along with postback data, so your bot knows exactly which option was tapped. Suggested actions open the phone's own apps: the dialer, the browser or a webview, maps, the calendar, or the location picker to share a position.
Card suggestions stay attached to the card. Chips appear in a scrolling row under the latest message and disappear once the customer taps one or replies, so use them for next steps such as "Talk to an agent" or "Stop messages". Since November 2025, open URL actions must use http:// or https:// links.
Verified sender and SMS fallback
Every RCS business agent is verified before launch: Google and the carriers check the brand, logo and use case, and the conversation shows the brand name with a verified badge. That trust signal is a large part of why RCS messages get higher engagement than plain SMS.
Not every phone or network supports RCS, so production traffic needs a fallback. The SMS version should carry the essentials and a link. One SMS holds 160 GSM-7 characters or 70 UCS-2 characters; longer texts are split into parts of 153 or 67 characters, each billed as one message. Arabic text, emoji and even curly quotes force UCS-2, so the builder counts parts and can swap typographic characters for plain ones.
About the exported JSON
The export follows the shape of an RBM AgentMessage contentMessage, with a standaloneCard or carouselCard, card suggestions and message-level suggestions. Media URLs are placeholders and postback data is generated from the button text. It is illustrative: use it to brief developers or compare with your provider's API.
With OmniChannels.ai you send the same card, carousel and suggestions through one REST API or a campaign, with automatic SMS fallback and delivery reports for both channels.
