Send a form to a recipient over SMS or RCS, or mint a standalone submission URL.

Pass form as either an existing form id (form_*) or an inline { fields, ... } definition to mint a new form for this send.

The delivery channel is inferred from from:

• from: "agent_*" → RCS (with optional SMS fallback)
• from: "+E.164" → SMS

When to is provided, Pinnacle dispatches a message whose body contains the submission URL and the recipient is recorded on the response: submission.to echoes the same E.164 number and message_id is the id of the outbound SMS/RCS.

When to is omitted, no message is sent — submission.to and message_id are both null — which is useful for embedding the URL in your own outreach.

On completion, a FORM.SUBMISSION webhook event is delivered to webhooks subscribed to the sender. See Receiving Message, Call, and User Events.