Azure API management policy toolkit is a set of libraries and tools for authoring policy documents for Azure API Management. The toolkit was designed to help create and test policy documents with complex expressions.
Before the Policy toolkit, policy documents were written in Razor format, which is hard to read and understand, especially when there are multiple expressions. The feedback loop on new documents or even the smallest changes was very long, requiring a live Azure API Management instance, a policy document deployment, and manual testing through the API request.
The policy toolkit changes that. It allows you to write policy documents in C# language, which is more natural and doesn't require you to jump between C# and XML for expression creation. Creating policy documents in C# also brings the advantage of using simple C# code for unit testing of policy documents.