Built by someone who actually plays.
Most Clash tools are built by developers who do not play, or run by players who cannot build. ClanWarden is one person doing both.
Four places you can see it
Not opinions about the product. Specific decisions that a non-player would have got wrong.
The boring but honest part
The player review, the roast, the boards, the base library and the streamer queue are free and need no account. The clan manager asks for an email so your war history has somewhere to live, and that is free too. Nothing joins your clan, nothing gets installed, and every number comes from Supercell's official API using tags that are already public in game.
ClanWarden is unofficial fan content and is not affiliated with, endorsed by, or approved by Supercell. The verdicts are my opinion, and the engine that produces them is mine to answer for. What is stored and why is written out in the policies.
Go and get judged
Paste a tag and you will have the verdict before you finish reading it. No login, no install, no bot in your clan.