The API Service of a full node enables a read-only query API that is useful for many tools such as dashboards, wallets, and scripting in general.
The API Service is configured in ~/.akash/config/app.toml and can be enabled in the [api] section:
[api]
enable = "true"
By default, the service listens on port 1317, but this can also be changed in the [api] section of app.toml.