Read the Swagger documentation of the Kimai 2 API in your Kimai installation at
As example you can have a look at the API docs for the demo installation at https://demo-v2.kimai.org/api/doc.
You need to login to see them, credentials can be found here.
Or you can export the JSON collection by visiting
/api/doc.json. Save the result in a file, which can be imported with Postman.
When calling the API you have to submit two additional header with every call for authentication:
X-AUTH-USER- holds the username or email
X-AUTH-TOKEN- holds the users API password, which he can set in his profile
If you develop your own extension and need to use the API for logged-in user, then you have to set the header
which will allow Kimai to use the current user session and not look for the default token based API authentication.