REST API
A REST API is an HTTP interface that organizes operations around resources and uses standard methods to create, read, update, or delete them. REST is an architectural style rather than a single protocol or file format.
How a REST API works
Each resource is represented by a URL, such as an agent, call, or contact. A client sends an HTTP request with a method that describes the intended action. The server returns a status, headers, and usually a structured response body. JSON is common, but REST does not require it.
REST requests are generally stateless: each request includes the information the server needs to understand it, rather than depending on a private conversational session with that client. Authentication credentials, resource identifiers, filters, and request bodies make the operation explicit. This property makes requests easier to route and retry, although clients must still avoid repeating actions that are not idempotent.
A well-designed API documents its resource shapes, validation rules, pagination, error responses, rate limits, and versioning policy. Access should be limited through scoped credentials, and sensitive values should not be placed in URLs where they may be copied into logs.
Why it matters for AI phone calls
A REST API gives teams a programmable way to manage a voice system and exchange data with it. A business application might create or update an agent configuration, retrieve a completed call record, start an approved outbound workflow, or attach a result to an internal customer record.
REST is most useful when a client initiates the exchange. It can query current state whenever needed, but frequent polling wastes work and delays reaction to new events. Webhooks complement REST by notifying the client when something changes; the client can then use the API to retrieve or update the relevant resource.
REST is also distinct from a live media channel. A phone conversation may require continuous, low-latency audio or event delivery, while a REST request represents a bounded operation with a response. WebSocket or media-specific protocols are often better suited to that continuous path.
Before integrating, teams should define which system owns each record, how credentials are stored, which actions can be retried safely, and how partial failures are reconciled. Those decisions prevent duplicate calls and conflicting updates.