When working with APIs, it is often necessary to create new objects, such as users, posts, or products. After creating these objects, it is crucial to return the ID of the newly created object for tracking and management purposes. Here are some tips on how to return the ID of an object created in an API:

1. Use a unique identifier for the object: When designing the API, make sure to use a unique identifier for each object that is created. This could be an auto-incrementing integer, a UUID, or any other unique identifier that can be used to distinguish one object from another.

2. Include the ID in the API response: When a new object is created in the API, make sure to include the ID of the object in the response. This could be done by adding a 'id' field to the JSON response that contains the ID of the newly created object.

3. Handle errors gracefully: In case of any errors during the object creation process, make sure to handle them gracefully and provide meaningful error messages to the client. This could include returning a specific error code along with a descriptive error message to help the client understand what went wrong.

4. Use proper HTTP status codes: When returning the API response, make sure to use proper HTTP status codes to indicate the success or failure of the object creation process. For example, use a 201 Created status code to indicate that a new object has been successfully created, and include the ID of the new object in the response.

5. Provide documentation: Lastly, make sure to provide clear documentation on how to interact with the API, including how to create objects and how to retrieve the ID of newly created objects. This can help developers understand how to work with the API and make the most of its features.

By following these tips, you can ensure that the process of creating and retrieving the ID of objects in your API is smooth and efficient, making it easier to track and manage objects in your system.