Customer Cards Documentation

This page is intended for a technical audience that will be implementing a Customer Card API. Check out the Customer Cards page for an overview.

Protocol overview

Customer Cards are not proactively loaded, all of it is just-in-time and pulled when required. This means that if your APIs are slow then users of the Support App will see a loading spinner over the card.

The protocol is as follows:

  1. When a user in Plain opens up a customer's page the cards are loaded.
  2. Plain's backend figures out which cards can be returned from the cache and which cards need to be loaded. On the first load of the customer this would be all cards.
  3. It calculates how many requests it needs to make (see request deduplication for details).
  4. Your APIs are then called with the customer's details, so you can look up the customer's data in your systems (see request section for details).
  5. Your APIs then return Customer Cards that consist of Plain UI components (see response section for details).
  6. The cards are cached based on either an explicit TTL value in the response or the TTL in the card settings.
  7. Cards are shown to the user in Plain.
  8. Users can manually reload the card at any time in which case only that one card will be requested from your API.

A few limits to be aware of:

  • Your API must respond within 4 seconds, or it will time out. See retry strategy for details on how timed-out requests are retried.
  • You can have a maximum of 25 Customer Cards per workspace configured.
  • Card keys must be unique within a workspace. A key can only contain alphanumeric, hyphen, and underscore characters (regex: [a-zA-Z0-9_-]+).

Creating a Customer Card

To create a Customer Card head to SettingsCustomer Card and enter the following details:

  • Title: This will be displayed as the title of the card so even if the card fails to load users know which card is errored.
  • Key: The link between this config and your API. A key can only contain alphanumeric, hyphen, and underscore characters (regex: [a-zA-Z0-9_-]+)
  • Default time to live (seconds): By default how long Plain should cache Customer Cards. The minimum is 15 seconds, maximum is 1 year in seconds (31536000 seconds).
  • URL: The URL of your API endpoint that will be built to return Customer Cards. Must start with https://.
  • Headers (optional): The headers Plain should pass along when making the request. While this is optional it is highly reccommend to add authorization headers or other tokens that authenticate the request as your API will be returning customer data.

To get you started quickly, we've created a few example Customer Cards that you can configure and see how they look in your application. All example cards are available in our open-source repository: team-plain/example-customer-cards (opens in a new tab)

Here is one you can try right now:


Plain will make the following request to your backend:

  • Method: POST
  • URL: the URL you configured on Customer Card settings page.
  • Headers:
    • All the headers you provided on Customer Card settings page. This should typically include authentication headers.
    • Content-Type: application/json
    • Accept: application/json
    • Plain-Workspace-Id: the ID of the workspace the customer is in. This is useful for logging or request routing.
    • User-Agent: Plain/1.0 (;
  • Body:
    • cardKeys: an array of card keys being requested
    • customer: an object with the customer's core details
      • email: the email of the customer
      • externalId (optional): if the customer has an externalId then it will be sent, otherwise it is null.

Example request body:

  "cardKeys": ["plan-details", "subscription-status"],
  "customer": {
    "email": "",
    "externalId": "your_user_id_795BFCD5-130F-4E72-BD46-14F717BE0830"

Request deduplication

If you configure multiple Customer Cards that have the same API details then Plain will batch them and make only one request.

The request deduplication logic for Customer Card configs is:

  • The following config properties are ignored: Title, Card key, Default TTL
  • API URL: Leading and trailing whitespaces are trimmed and then compared. This is case sensitive.
    • For example, these URLs would be considered different:
  • API Headers: Order of headers does not matter
    • Header name: Leading and trailing whitespaces are trimmed and then compared. This is case insensitive.
      • For example, these header names be considered the same:
        • Authorization
        •    authorization   
    • Header value: No processing done, compared as is (be careful with any extra whitespace characters)
      • For example, these header values would be considered as different:
        • Bearer my-token
        • bearer my-token
        •    bearer my-token   



For each key requested a corresponding card MUST be returned in the response, otherwise an integration error will be returned for that card.

Any extra cards in the response will be ignored.

Your API must respond with a 200 status code or the response body won't be processed and will be treated as an error.

The response body must be a JSON object with:

  • cards: an array of cards. Every cardKey requested should have a corresponding key returned. Any extra returned cards will be ignored.
    • key: the requested key
    • timeToLiveSeconds (optional, nullable): can either be omitted or null. If provided it will override the default time to live value. This allows you to control caching on a case-by-case basis.
    • components (nullable): null to indicate that the card has no data or an array of Plain UI Components.

Example response body for a card cached for 1 hour:

  "cards": [
      "key": "plan-details",
      "timeToLiveSeconds": 86400,
      "components": [
          "componentRow": {
            "rowMainContent": [
                "componentText": {
                  "text": "Plan",
                  "textColor": "MUTED",
                  "textSize": "M"
            "rowAsideContent": [
                "componentBadge": {
                  "badgeLabel": "Starter",
                  "badgeColor": "YELLOW"

Example response body for a card that has no data and should not be displayed and TTL omitted:

  "cards": [
      "key": "plan-details",
      "components": null

Retry strategy

Errors are classified into two categories:

  1. Retriable errors: these are transient issues where retrying once is appropriate
  2. Integration errors: these are typically programming or configuration errors. These errors won't be retried and cached for 5 minutes.

Retriable errors

The following errors are retried once after a 1-second delay:

  • HTTP 5xx response status code
  • HTTP 429 Too Many Requests response status code
  • The request times out after 4 seconds.
  • Plain fails to perform the request for some reason

Retriable errors are not cached, therefore if the cards are requested again via the Support App they will be re-requested.

Integration errors

The following errors are not retried:

  • All HTTP 4xx response status codes except for HTTP 429 Too Many Requests response status code.
  • A card key is missing in the response for example, if subscription-details is requested but the cards array in the response doesn't have an element with subscription-details key.
  • The response body does not match the expected schema documented in response.

Integration errors are cached for 5 minutes and usually indicate a programming or configuration error.

Users can manually refresh a card in the UI in which case the card will be requested again.