Hello,
We have experience with integrating several APIs, be they public (Facebook, Twitter, LinkedIn, Flickr, Vimeo, Google, YouTube, aWeber, PayPal APIs and more) or private. Thus, integrating your application with Merchant Web Service will work smoothly, as long as they have a proper documentation.
We would love to discuss more about it.
Please let me know if you have questions and I'll get back to you in a timely manner.
Best regards,
Alexandra Vlasceanu
Solution Finder - Barandi Solutions