Whenever I am asked to give a quote for a project that involves a remote REST API, I become very cautious.
Most of the REST API's I worked with had a documentation, but it usually turned out to be very basic (I may not need prose texts, but I don't have a crystal ball either), with the real complexity hidden somewhere and requiring long discussions with the API devs.
I shot myself in the foot several times already with this.
But clients, especially new ones, insist on a project budget.
I understand that all projects involving 3rd party software potentially have this problem. But it am under the impression that REST API devs are especially lazy with proper documentation, there is no source code that could provide you with clues, and there usually is no community for API's that are much smaller than Paypal or Amazon.
Since almost all new projects involve a remote REST Api of some sort, my question is: How do you deal with this?