I would rather not let agent use checkout. I think they are not "smart" enough to tell scam from real website apart. Even recently Claude/Opus referred me to scammers website telling me to buy a product there.

Agents checkout + risk of prompt injection => big nop!

What is even the legal basis here? Can the agent sign contracts on your behalf? What if it is tricked by the vendor into signing for a monthly subscription you never wanted?