The on-line API documentation explains the data that modules expect and return on their APIs. The associated list of endpoints will also assist.
See Wiki Working with FOLIO APIs. Get help in the FOLIO Slack #learning-apis channel.
To connect to the APIs, there are several software options:
curl
The Okapi Guide has detailed examples and explanations how to use APIs with command-line tool curl.
okapi-curl
The okapi-curl is a shell script that wraps curl.
Okapi CLI
The okapi-cli is a command-line interface written in Java.
OkapiClient
The OkapiCLI.py is a command-line interface written in Python.
Stripes CLI
The stripes-cli is a command-line interface written in JavaScript that can connect to back-end APIs and help front-end developers that use FOLIO’s User Interface framework Stripes.
Postman
The folio-api-tests Github repository contains Postman collections for the APIs of some FOLIO modules. Use them with Postman or Newman.
HTTPie
HTTPie has a command-line tool and also a user interface.