Very gentlemanly, although until I've built it I have no right to even ask!

It's a marketplace to seek and give Attestations for any other Nostr event. It will also help surface Attestations before there is wider client support.

So, for your use case, if you had some kind of 'contract obligations met' event, each party (and even a 3rd part witness) could Attest to that core Subject Event with an Attestation Event.

More detail here: