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v2

latestOpenAPI 3.1.02026-08-075421692.0 MB
Messages

Create conversation

Initiate a new direct message conversation with a specified user. If a conversation already exists with the recipient, the message is added to the existing thread.

Supported platforms: X/Twitter, Bluesky, Reddit, WhatsApp, SMS, and Slack. Other platforms return PLATFORM_NOT_SUPPORTED.

Slack: pass a workspace member id as participantId (list them with GET /v1/accounts/{accountId}/slack-members). Zernio opens the DM channel with that member and sends the message; the thread then behaves like any other Slack conversation in the inbox. The member must belong to the connected workspace.

WhatsApp: this is the endpoint for sending an approved template message to a phone number. Provide templateName, templateLanguage, and templateParams (variable values for the text header, body and dynamic URL buttons, in that order), with the recipient phone in participantId. A template is required because WhatsApp does not permit freeform messages to open a conversation; a missing template returns TEMPLATE_REQUIRED. Templates with media headers (image, video, document) are handled automatically: Zernio reads the approved template definition and fills the header at send time with the template's approved sample asset. To send a DIFFERENT asset per message (e.g. a distinct invoice PDF for each recipient), pass the headerMedia field with a public link (or a Meta media id); it overrides the sample for that send. Calling this for a number you already have a thread with simply sends the template into that thread, which also makes it the way to re-engage a contact after the 24-hour customer-service window has closed. Once the recipient replies (opening the 24h window), send freeform messages with the send-message endpoint (POST /v1/inbox/conversations/{conversationId}/messages). Template fields are accepted on the JSON body only, not on multipart requests. Alternatively, WhatsApp Business Accounts eligible for Meta Direct Send can open a conversation with a business-initiated utility text message and no template: pass category: 'utility' together with message (and no templateName). See the category field below.

DM eligibility (X/Twitter): Before sending, the endpoint checks if the recipient accepts DMs from your account (via the receives_your_dm field). If not, a 422 error with code DM_NOT_ALLOWED is returned. You can skip this check with skipDmCheck: true if you have already verified eligibility.

X API tier requirement: DM write endpoints require X API Pro tier ($5,000/month) or Enterprise access. This applies to BYOK (Bring Your Own Key) users who provide their own X API credentials.

Rate limits (X/Twitter only): X's DM API enforces 200 requests per 15 minutes, 1,000 per 24 hours per connected X account, and 15,000 per 24 hours per X developer app (shared across all DM endpoints). These limits do NOT apply to other platforms. WhatsApp sends are governed by Meta's per-number messaging tiers (unique business-initiated conversations per 24 hours) and per-number throughput instead.

post/v1/inbox/conversations

Request body

accountIdstring required

The social account ID to send from

participantIdstring

Recipient identifier. For X this is the numeric user ID; for WhatsApp and SMS, the recipient phone number in international format (digits, country code included); for Slack, the workspace member id (e.g. U01ABCDEF). Provide either this or participantUsername.

participantUsernamestring

Recipient handle/username — an X or Bluesky handle (with or without @) or a Reddit username (with or without u/). Resolved via lookup. Provide either this or participantId.

messagestring

Text content of the message. At least one of message, attachment, or (for WhatsApp) templateName is required. Required when category is set (a Direct Send utility message is a text message).

skipDmCheckboolean

X/Twitter only. Skip the receives_your_dm eligibility check before sending. Use if you have already verified the recipient accepts DMs.

templateNamestring

WhatsApp only. Name of the approved template to start the conversation with. Required for WhatsApp unless category is used instead (Direct Send). Cannot be combined with category.

category'utility'

WhatsApp only (Meta Direct Send). Combined with message and without templateName, starts the conversation with a business-initiated UTILITY message and no pre-approved template; Meta matches or auto-creates a template asynchronously. The WhatsApp Business Account must be eligible for Direct Send, otherwise the send fails with an error telling you to use an approved message template instead. Cannot be combined with templateName (templates are already categorized at creation). Utility messages only; marketing content is not allowed under this category. Accepted on the JSON body only, not on multipart requests.

templateLanguagestring

WhatsApp only. Template language code (e.g. en_US).

templateParamsstring[]

WhatsApp only. Template variable values as one flat array, in the order the variables appear across the whole template: text-header variables first, then body variables, then one value per dynamic URL button (in button order). Works with positional placeholders ({{1}}, {{2}}, ...) and with named placeholders ({{name}}, {{company}} - how Meta Business Manager creates templates), where values fill the named slots in order of appearance. Example - a body with {{1}}, {{2}} plus a URL button https://example.com/{{1}} takes three values: [body1, body2, buttonSuffix]. Media headers (image, video, document) are filled automatically from the approved template and take no value here (use headerMedia to override the header asset per send).

Response

Conversation created successfully

successboolean

Example response

{
  "success": true
}