Quick Answer

A 400 status code or a "reason phrase must not contain new-line characters" error from POST /api/v2/assignments/CreateAssignment, in an integration that previously worked, has been reported as linked to a change in the request payload's ContentAssignments object - confirm your payload structure against your own live Swagger/OpenAPI reference before changing your integration.

What This Article Helps With

This article is for technical/IT contacts whose integration calls POST /api/v2/assignments/CreateAssignment and has started returning errors, including on an integration that previously functioned correctly.

Symptoms

Calls to POST /api/v2/assignments/CreateAssignment return a 400 status code, sometimes with an error message stating "The reason phrase must not contain new-line characters." This typically appears on an integration that was previously functioning correctly.

Cause

The POST /api/v2/assignments/CreateAssignment endpoint itself is confirmed to exist in the Platform API. A reported cause of this specific error is a change to the required request payload structure following a product release — specifically, within the ContentAssignments object. Available documentation does not independently confirm the exact current request schema for this endpoint; confirm it against your own live Swagger/OpenAPI reference before relying on the payload structure described below.

Resolution

One reported fix for this error is updating the ContentAssignments object in your request payload as follows:

1. Replace the ContentIds array (an array of strings) with a ContentIdsAndOrder array (an array of objects).
2. Within each object in the ContentIdsAndOrder array, include a ContentId field for the content identifier.
3. Optionally, include an Order field within the same object.
4. Confirm there are no blank lines or embedded line breaks in your payload, particularly before the DueDate field or within an EmailTemplate Body value — these have been reported as contributing to the "reason phrase" error specifically.

For example, a payload using the reported older format:

{
  "ContentAssignments": [
    {
      "AssigneeId": "string",
      "AssignorIds": ["string"],
      "ContentIds": ["string"]
    }
  ],
  "EmailTemplate": { "Subject": "string", "Body": "string" },
  "DueDate": "YYYY-MM-DDTHH:MM:SS.SSSZ"
}

would become, in the reported updated format:

{
  "ContentAssignments": [
    {
      "AssigneeId": "string",
      "AssignorIds": ["string"],
      "ContentIdsAndOrder": [
        { "ContentId": "string", "Order": 0 }
      ]
    }
  ],
  "EmailTemplate": { "Subject": "string", "Body": "string" },
  "DueDate": "YYYY-MM-DDTHH:MM:SS.SSSZ"
}

These examples illustrate the reported change; confirm the exact field names and structure against your own live Swagger/OpenAPI reference for your tenant before updating a production integration.

After updating your payload, resend the POST /api/v2/assignments/CreateAssignment request and confirm it returns a successful response rather than a 400 status code, and that the assignment appears as expected in Pinnacle Series.

Helpful Tips

• Test payload changes against a non-production tenant, or with an API development tool such as Postman, before updating a live integration.
• If the error persists after confirming your payload against the live schema, log a support ticket with your request payload and the exact error response.

Still Need Help

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