Custom Field GID changes on each task.

[Daniel_Iversen]

Sure!

Here’s how to create a “global” Custom Field via the UI first:

Custom fields

And for the API to then to be able to assign it to tasks, you have to first add the Custom Field to the project (before trying to use it on tasks), as per @Matt_Bramlage’s instructions here:

Create a task with an existing custom Field

I can verify that there are no custom fields set on that project. If you’re looking to do this in the API, you can POST a request to /projects/:project_id/addCustomFieldSetting, which will associate the custom field with the project. Then it should be possible to set the value of the custom field on the task as above.

Hope that helps!

Cheers,
Daniel