gmail-draft

gmail draft create --to <addr> --subject <s> --body-file <file> [--cc][--bcc][--attach]
gmail draft update --draft-id <id> --to <addr> --subject <s> --body-file <file>
gmail draft list [--query "<gmail query>"] [--max 25]
gmail draft send --draft-id <id>
gmail draft delete --draft-id <id>

--json gives the Envelope on any of them.

When to draft instead of send

Draft by default. Send directly only when the user has seen the words and said to send them. Drafting is the whole reason this is a separate skill from gmail-send: it turns an irreversible action into a reviewable one, and the user can finish it in Gmail on their phone.