Supported channels for this REST operation: WhatsApp only. Use a conversation ID from a relevant conversation response for that workspace and channel; do not substitute a contact ID. A target accepted by another endpoint does not imply this operation supports that channel. The customer-service/reply window and channel permissions must still allow the send.

• Status code 200 means the message was accepted by WATI, not delivered yet.
• To know if a message failed, listen to the Session Message Failed webhook.
• To know if a message succeeded, listen to Delivered/Read/Reply webhooks.

Permissions

For API access tokens and OIDC tokens, satisfy at least one of: api, conversationsv3:write. API access tokens may satisfy a listed scope through the configured scope hierarchy; OIDC tokens are checked against their scope claims. Legacy JWT authentication does not use this scope check. Authentication, role, tenant, and applicable feature or plan checks still apply. For HTTP 403, check the credential type, applicable scopes, roles, and workspace access; 403 does not always mean a missing scope. Authentication/authorization failures do not guarantee a JSON response body.