Trying to build a custom chat client using the Guest API instead of the widget. I’m hitting POST /api/v2/conversations/messaging/guest/conversations/{{conversationId}}/messages with a valid guest token, but I keep getting a 500 error. The payload is standard:
{
"from": {"id": "guest-id"},
"text": "Hello"
}
The conversation was created successfully via the same API just seconds before. Any ideas what’s breaking?
That 500 is usually a silent killer. It’s not your token. It’s the payload structure. The Guest API is notoriously picky about what you send in the message body, and sending just from and text often trips up the backend validation, especially if the conversation was just created and the guest identity hasn’t fully propagated in the cache.
Try adding the to field explicitly. Even though it’s a guest conversation, the API expects the target address to be present in the message payload for routing consistency. Also, make sure you’re not sending the id field in the request body. The server generates that. If you send it, it might conflict with internal state checks.
Here’s a working curl example using the Node.js SDK’s underlying HTTP client logic. Note the to field and the absence of id:
curl -X POST "https://api.mypurecloud.com/api/v2/conversations/messaging/guest/conversations/{{conversationId}}/messages" \
-H "Authorization: Bearer {{guestToken}}" \
-H "Content-Type: application/json" \
-d '{
"to": {"id": "platform-user-id-or-queue-id"},
"from": {"id": "{{guestId}}"},
"text": "Hello"
}'
If you’re using the platformClient in Node, the createConversationMessagingGuestConversationMessage method handles this, but you still need to map the payload correctly.
const body = new PureCloudPlatformClientV2.Message();
body.to = { id: 'your-queue-or-user-id' };
body.from = { id: guestId };
body.text = 'Hello';
// Ensure you're not passing an ID
// body.id = undefined;
await messagingApi.createConversationMessagingGuestConversationMessage(conversationId, body);
Check your server logs. If it’s still 500, it’s likely a backend bug with the specific conversation state. But 90% of the time, it’s just missing the to field. The docs are sparse on this. They imply the from is enough for guest contexts, but the validation layer disagrees. Always include the destination.