The URL parameter "categoryId" can be used in two ways:

• use the unique ID of the service category assigned by TIMIFY ("categoryId"). In this case, you don't need the QUERY parameter "external"
• use the "externalId" that you added to this service category. In this case, you need to add the parameter "external" ( for ex.: /?external=1) so the Developer API will search by your "externalId" and not by "categoryId" assigned by TIMIFY

You can add "externalId" to the service category with the Developer API endpoints POST /services/categories and PATCH /services/categories/:categoryId