Set Participant Data payload serialization failure in CXone Studio

Architect & Flows
1
  • CXone Studio v2.4.1
  • REST API integration via GetRESTProxy
  • Asia/Singapore region

Trying to understand why the Set Participant Data action consistently rejects my custom variable payload. I am constructing the JSON string manually via ASSIGN and passing it to the data action, yet the flow logs indicate a validation error on the schema structure. The payload follows the standard format:

{"custom_attributes": {"tier": "gold", "source": "ivr"}}

Is there a specific escaping requirement for the nested object when injecting this string into the Set Participant Data node?

2

How I usually solve this is by using the .NET SDK’s FlowsApi to validate the FlowParticipantData model before serialization, as manual JSON construction often misses the required type field for custom attributes.

  • Check if type is set to string or number
  • Verify key matches the flow variable name exactly
  • Ensure the payload is not nested deeper than one level
3

const payload = {
key: “myVar”,
value: “test”,
type: “string”
};

Have you tried explicitly defining the `type` field in your JSON object? **Studio** requires this for schema validation. Manual string construction often omits it.
4

The official documentation states that manual ASSIGN string construction is the primary cause of schema validation failures in Set Participant Data. Studio expects a strict JSON object structure, not a raw string. When you pass a stringified JSON to the data action, the parser fails to map the type field correctly.

I recommend using the JsonEncode expression function instead. This ensures proper escaping and structure.

{{JsonEncode({
 "key": "myVar",
 "value": "test",
 "type": "string"
})}}

This approach bypasses manual syntax errors. Also, ensure the key matches the flow variable name exactly. Case sensitivity matters. If the variable is MyVar, the key must be MyVar. Mismatched keys cause silent failures in some versions.

  • Verify type matches the variable definition
  • Check for special characters in key
  • Review flow logs for 400 Bad Request details
5

It depends, but typically the issue stems from treating the Set Participant Data input as a raw string rather than a structured object within the CXone Studio execution context. The suggestion above regarding JsonEncode is correct, but you must ensure the object hierarchy matches the SDK’s internal serialization expectations. In my Kotlin integration with the Web Messaging SDK, I have observed that manual string concatenation often introduces invisible whitespace or incorrect escape sequences that break the schema validator.

Instead of ASSIGNing a string, construct the map directly. The API expects a specific structure for custom attributes. See the Flow Participant Data API docs for the exact schema.

{
 "type": "string",
 "key": "myVar",
 "value": "test"
}

Ensure the key matches the variable definition in your flow configuration exactly. If you are passing this via REST, verify the Content-Type is strictly application/json.