Are you looking for an API to read your company and personal contacts? If so, check out these APIs
Using the RingCentral Phone for Desktop, you can dial or receive test calls, send and receive test SMS or Fax messages in your sandbox environment.
Download RingCentral Phone for Desktop:
Tip: switch to the "sandbox mode" before logging in the app:
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Salesforce Integration fails if more than one contact shares the called phone number (for instance, when calling a company phone number)
/account/~/directory/entries not returning IVR Menus
How to create/update exisitng extensions using the API? Or how could I add internal contacts?
High Volume SMS web app imported fields not working.