We keep adding more information to the site registration, however initial registration is sent as GET request length may be limited.

In fact, I have found a registered site with the name:
АНО "ДПО "Институт повышения квалификации специалистов профессионального образования"; АНО "Санкт-Петербургский научно-исследовательский институт педагогики и психологии высшего образования"; АНО ВО "Санкт-Петербургский педагогический институт"

see https://moodle.net/sites/index.php?country=RU

This site would not be able to register if it was happening now because the total query length would be 2107 characters (even without descriptions, alternative emails, etc)
Also token is appended to the end of request.

To minimise changes on moodle.net side (processing of initial registration is very complicated), I can recommend the following:

• send only minimum information in the initial request
• right after registration is confirmed send a WS request updating registration with full data

P.S. The actual solution submitted is slightly different:

• send token as the very first parameter in query string
• send important/required fields (policyagreed, country, language, subscription emails) first, followed by other fields including name. If the URL is truncated by the browser, we don't loose important information and during the next registration update all fields will be sent properly (update registration task uses POST)