Is it possible to inject OpenTelemetry trace headers into the participant address for outbound calls? I am receiving a 400 error when attempting to pass the W3C trace context via the from or to address parameters.
{
"code": "bad_request",
"message": "Malformed participant address"
}
The standard JSON payload works fine without the headers. How should I structure the request to avoid schema validation failures?
The root cause here is the Conversations API strictly enforcing the participantAddress schema, which expects a standard URI format (e.g., tel:+6512345678 or sip:[email protected]). The from and to fields in the outbound call payload are not designed to accept arbitrary HTTP headers or OpenTelemetry trace context strings. Injecting trace data directly into these URI fields triggers a schema validation failure, resulting in the 400 Bad Request.
To propagate trace context for outbound calls, you must use the customHeaders field within the participant object, not the address itself. The SDK handles the serialization of these headers correctly when constructing the OutboundCallRequest. Here is the correct Python SDK pattern for injecting trace headers while maintaining valid participant addresses:
from purecloud_platform_client import PureCloudPlatformClientV2
body = {
"to": {
"participantAddress": "tel:+6598765432",
"customHeaders": {
"traceparent": "00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-01"
}
},
"from": {
"participantAddress": "tel:+6512345678"
}
}
# Ensure client is authenticated with callcenter:outboundcalls:modify scope
api_instance = platform_client.conversations_api
try:
response = api_instance.post_conversations_calls(body=body)
print(f"Call initiated: {response.id}")
except Exception as e:
print(f"Error: {e}")
The traceparent header is passed via customHeaders, keeping the participantAddress clean. This aligns with the API contract and avoids schema violations. Note that not all downstream telephony providers honor custom headers, so verify trace propagation in your specific routing configuration.
Warning: The callcenter:outboundcalls:modify scope is required. If you see a 403 error after fixing the payload, inspect your OAuth token scopes directly in the notebook using client.oauth_client.get_access_token() to ensure the correct permission is present.