There are no plans to support calling a generic REST APIs from a flow for now, since there are many technical caveats with these connections that cannot be solved without coding. Since Zapier allows you to add blocks of code into your zaps, you can very easily use them to achieve any result. For example, some proprietary way of encoding data would be a good example. We actually advice to use Zapier over SOAP if you can.
With SOAP, there is a very clear and formal way that all calls must be handled. This means that Triggre can read this information and guarantee the correct delivery of the data. For REST APIs this is not the case. They are free-format and as you can very quickly see if you read a few of them, every single one has a slightly different way of handling things. This means we would never be able to guarantee your connection would still work if we update our platform.
Zapier solves this problem by being the translator. If we update Triggre, all we need to do is make sure we correctly talk to Zapier. All other apps that are linked to Triggre through Zapier, are then unaffected. The same holds when any other application provider changes their interface. We don’t need to know about it, because they will make sure it still works with Zapier and therefore it will still work with Triggre.
I hope this explains why we chose to support only Zapier to connect other SaaS applications. It’s a matter of maximizing reliability and convenience.
Here are some great articles/pages about using Zapier with any proprietary REST API: