No because most apps won't be Farcaster wallets and won't have access to the ECDSA key.

Understood, and that’s my bad, it’s been a while since I visited the “advanced” settings in Warpcast. Didn’t realize this is where you can manage the connections to apps.

Interesting! So when building a farcaster protocol client, you could build a farcaster wallet(manage the key) or just farcaster app(relying on warpcast) Does this mean it's impossible to just use metamask to manage your farcaster key/fid ?

Searchcaster