How to use SonarQube web API?

http://localhost:9000/web_api/ can be helpful, explain the parameters, have examples of response and trace changes with the Sonarqube versions.

The SonarQube web API lives under the /api context path, as per the SonarQube documentation, along with the section and the operation (which you seem to be missing).

As an example, to search for issues on localhost running on port 9000, send a GET to http://localhost:9000/api/issues/search?pageSize=500&componentKeys=YOUR_COMPONENT and parse the JSON response.

You may need to provide authorization as well, which is sent as either a BASIC username password combo, or an access token which you can retrieve via the web client.