To send custom requests you can use the lower-level octokit.request() method

octokit.request("GET /");

The baseUrl, headers and other defaults are already set. For more information on the octokit.request() API see octokit/request.js

All the endpoint methods such as octokit.repos.get() are aliases of octokit.request() with pre-bound default options. So you can use the @octokit/request API to get the default options or get generic request option to use with your preferred request library.

const defaultOptions = octokit.repos.get.endpoint.DEFAULTS;
const requestOptions = octokit.repos.get.endpoint({
owner: "octokit",
repo: "rest.js",
});

Note that authentication is not applied when retrieving request options from the *.endpoint APIs.