Answer:
One service with great API documentation that doesn't integrate with Zapier is Twilio, a cloud communication platform.
Step-by-step explanation:
Twilio provides a comprehensive and well-documented API for programmatically sending and receiving text messages, making phone calls, and more.
For Twilio's API, you could create a trigger on Zapier using the "New Incoming SMS" event. This trigger would activate a Zap. a workflow on Zapier, whenever a new SMS message is received on your Twilio number.