# The structure of Twilio's OpenAPI Spec

Upon visiting either the [JSON](https://github.com/twilio/twilio-oai/tree/main/spec/json) or [YAML](https://github.com/twilio/twilio-oai/tree/main/spec/yaml) folders of `twilio-oai/spec`, you'll notice a long list of files instead of a single specification. This is because Twilio's API spans multiple subdomains, such as `api.twilio.com`, `accounts.twilio.com`, `flex-api.twilio.com`, and many others.

Each file corresponds to one of these subdomains, which can be determined by looking at the `servers` property of any of the described endpoint paths in a given file.

For example, in `twilio_acounts_v1.json`, you'll find the following top-level property:

```json
  "servers": [
    {
      "url": "https://accounts.twilio.com"
    }
  ],
```

This indicates that the file corresponds to the `accounts.twilio.com` subdomain. This same process can be applied to all spec files.