What a container tracking API actually gives you

Tracking APIs are sold on carrier counts. The count is the least interesting part.

The shape of the data

You send a reference, a container number, bill of lading or booking. You get back a shipment object: the carrier, the vessel and voyage, the route, and a list of events. Each event has a type, a location, a timestamp and a flag for estimated or actual.

That is essentially it. Everything else is packaging.

Where the value is

Every carrier names things differently. One calls it gate out, another discharge from terminal, a third uses a numeric code. A good API maps all of that into one vocabulary so your code has one branch instead of forty.

That mapping is the product. Connecting to a carrier is a week of work. Maintaining forty mappings as carriers change their formats is a permanent job, and it is the job you are outsourcing.

The honest limits

An API cannot invent events. If a carrier does not publish transshipment loading, no provider will return it. Be suspicious of anyone claiming complete visibility across all carriers, because the underlying data does not exist for that claim to be true.

Ask instead what happens when two sources disagree, and whether anybody looks at the conflict before it reaches you.