Set Participant Data action payload structure for custom IVR variables

Architect & Flows
1

Is it possible to reliably pass custom variables from an IVR flow to a downstream external integration using the Architect Set Participant Data action without encountering serialization issues in the webhook payload?

We are instrumenting our Genesys Cloud flows with New Relic APM to track specific customer journey metrics. To achieve this, we need to capture custom attributes set during the IVR interaction and forward them to a Lambda function via a webhook. We are using the Set Participant Data action to define these variables within the flow.

Here are the steps to reproduce the issue:

  1. In Architect, we add a Set Participant Data action after the IVR menu selection.
  2. We define a custom variable named customer_tier with a string value (e.g., “Gold”).
  3. We route the interaction to a webhook action that POSTs to our AWS Lambda endpoint.
  4. The Lambda function logs the incoming JSON body to New Relic as a custom event.

The JSON payload received by the Lambda appears to truncate or omit the custom participant data fields, resulting in a 200 OK response but missing data in our NRQL dashboards. The expected payload structure includes the customData object, but it is often empty.

{
 "conversationId": "abc-123",
 "participantId": "def-456",
 "customData": {}
}

We have verified that the Set Participant Data action is executed by checking the flow trace logs, which show the variable assignment. However, the external webhook does not reflect these changes. Is there a specific timing constraint or payload format requirement for the Set Participant Data action to ensure the custom variables are included in the subsequent webhook request? We suspect the data might not be flushed to the participant record before the webhook trigger fires, but we lack documentation on the execution order of these actions within the same interaction lifecycle.

2

It depends, but generally…

The issue is rarely the Set Participant Data action itself. It is how the downstream webhook serializes the payload. Genesys Cloud sends participant data as a flat JSON object in the webhook body. If your Lambda expects nested objects or specific typing, you will hit serialization errors.

Error: JSON parse failed: Unexpected token o in JSON at position 1

Here is the correct pattern to ensure clean data flow.

  1. In Architect: Set your data in the Set Participant Data action. Use simple key-value pairs. Do not use complex objects.
  • Key: custom_metric_id
  • Value: {{contact.custom.metric_id}}
  1. In the Webhook Action: Ensure you are sending the body as application/json. The payload will look like this:
{
 "participant_data": {
 "custom_metric_id": "12345"
 },
 "contact_id": "abc-123",
 "type": "webhook"
}
  1. In your Lambda/Integration: Parse the participant_data object directly. Do not attempt to parse the entire webhook body as a single string if your framework does it automatically.
// Node.js Lambda example
exports.handler = async (event) => {
 const body = JSON.parse(event.body);
 const metrics = body.participant_data || {};
 
 // Safe access to your custom variable
 const metricId = metrics.custom_metric_id;
 
 console.log("Tracking metric:", metricId);
 return { statusCode: 200 };
};

Key Takeaway: Keep keys alphanumeric. Avoid spaces or special characters in the Set Participant Data keys. Genesys Cloud sanitizes some characters, which can break your downstream parsing logic. If you need complex structures, serialize them to a JSON string in Architect first, then parse in your integration.

Check your Open Messaging webhook logs if you are bridging this to a third-party channel. The payload structure differs slightly there. But for standard IVR to Lambda, the above works.

3

the flat json structure mentioned above is spot on, but i hit a snag when trying to access those custom keys in node. you have to dig into the participants array first. here is how i structured the webhook payload in architect to make sure the lambda receives the data correctly without null errors.

{
 "conversationId": "{{conversation.id}}",
 "participants": [
 {
 "id": "{{participant.id}}",
 "customAttributes": {
 "journeyStep": "{{participant.customAttributes.journeyStep}}",
 "queueName": "{{participant.customAttributes.queueName}}"
 }
 }
 ]
}

this worked for my migration tests. make sure your lambda handler checks for the existence of customAttributes before trying to parse it, otherwise you get undefined errors.