Is Warehouse management APIs are available in business central?

For Inventory Put-away, I would not treat it the same as the Warehouse Receipt process because the document flow depends on the warehouse setup of the Business Central location.

If the location is configured with Require Put-away but not Require Receive, Business Central uses the Inventory Put-away flow. If Require Receive is enabled, the inbound process moves through Warehouse Receipt instead.

For an external integration, creating a custom API page over the Inventory Put-away tables can expose the document data, but exposing the page itself does not automatically expose the standard posting action as an API endpoint.

For posting/registering the Inventory Put-away, I would normally implement a controlled custom API/action that calls the appropriate standard Business Central posting logic/codeunit rather than trying to reproduce the posting logic externally.

This is important because posting a warehouse activity updates several related warehouse and inventory records, so directly inserting/modifying the underlying tables through an API is not recommended.

So the approach I would suggest is:

• Create the Purchase Order through the standard API.
• Create/get the Inventory Put-away using standard Business Central logic based on the source Purchase Order.
• Expose the required Inventory Put-away information through a custom API if needed.
• For the Register/Post operation, expose a controlled custom endpoint that invokes the standard Business Central posting routine.

If you can share whether the location has Require Put-away, Require Receive and Bin Mandatory enabled, I can suggest the appropriate inbound flow and AL approach in more detail.