Legal One is a platform used by several Thomson Reuters products. Inside this family, you the APIs of products powered by the Legal One platform. The overall flow for the API usage, including the authentication, is the same regardless the product you are using to access it, we'll be able to find the documentation in the Tutorials section of the specific API.
With the Legal One API you can manipulate data in the Legal One product of our clients. The overall usage of the workflow is the same throughout the different Legal One products, what enables you to easily create integrations with the different Legal One products without having a lot of code changes.
You can check the endpoints available for the product in the Dev. Tools section of each API. Check the Tutorials section to learn how to use the API. Get started by choosing one of the available APIs in the Legal One Family.