By the way, here is the NIP for “zaps” (Lightning Invoice events).
To follow this same kind of structure, I think you’d put the slatepack in a “grin” tag, like how they put the LN invoice in the tags.
[
"bolt11",
"lnbc10u1p3unwfusp5t9r3yymhpfqculx78u027lxspgxcr2n2987mx2j55nnfs95nxnzqpp5jmrh92pfld78spqs78v9euf2385t83uvpwk9ldrlvf6ch7tpascqhp5zvkrmemgth3tufcvflmzjzfvjt023nazlhljz2n9hattj4f8jq8qxqyjw5qcqpjrzjqtc4fc44feggv7065fqe5m4ytjarg3repr5j9el35xhmtfexc42yczarjuqqfzqqqqqqqqlgqqqqqqgq9q9qxpqysgq079nkq507a5tw7xgttmj4u990j7wfggtrasah5gd4ywfr2pjcn29383tphp4t48gquelz9z78p4cq7ml3nrrphw5w6eckhjwmhezhnqpy6gyf0"
],
We could actually follow the spec of NIP-57 almost exactly the same. So you could send a slatepack in reply to a specific note (like tipping someone for a good post) or just generally to their account. And you could also include a note in the content that says what the money is for (this is like the fun part of Venmo where you have emojis etc).