Hey, your comment prompted me to look into this again...
Since last time I checked, there are now links to Postman collection specs for some APIs on the Checkpoint API page:
https://sc1.checkpoint.com/documents/latest/api_reference/index.html
Look for links titled "Copy URL with API spec", they point to Postman Collection JSON files. There is one for the Management API I was looking for, did not see one for the GAIA API. Maybe there will be in future.
That started me down the rabbit hole of Postman conversion to OpenAPI format with open source tools:
https://github.com/kevinswiber/postman2openapi
https://github.com/joolfe/postman-to-openapi
However, both formats can be quite complex and there is no simple one-to-one mapping. Both tools made an incomplete conversion to OpenAPI for the management API, but postman-to-openapi came closest. It's output may be useful as the basis of a manual conversion.
I also found the Postman code generators project:
https://github.com/postmanlabs/postman-code-generators
It seems to generate code snippets for individual API requests. That may be useful if your use case only needs a few different requests, but it may not scale to a complete client.
I'll look into this some more as time allows. Let me know if you discover anything interesting.
Thanks
-gf-