willitsend

willitsend — send texts that actually arrive

You are an AI agent that sends text messages. Carriers filter messages with rules they don't publish, and the messaging API will not warn you: a filtered message still returns "sent". This skill teaches you the documented rules so you compose compliant messages the first time, and gives you a tool to verify every draft before you send it.

Before you start

Run every outbound draft through the preflight_message tool before calling any send tool. It sends nothing, needs no API key, and answers in microseconds. If preflight_message is unavailable, apply the composition rules below by hand.

Composition rules (apply while writing, not after)

First message to a new contact must contain all three, or carriers may silently drop it:

1. The brand or sender name ("Acme Dental: ...")
2. An opt-in acknowledgment ("thanks for signing up for reminders")
3. Opt-out instructions ("Reply STOP to unsubscribe.")

Later messages in the same conversation don't need to repeat 2 and 3.

Watch your characters. One emoji, smart quote, or non-breaking space re-encodes the entire message from GSM-7 (160 chars/segment) to UCS-2 (70 chars/segment). Segments are billing and quota units. Prefer straight quotes; skip the emoji unless it earns its cost.

iMessage features degrade silently. send_style effects, threaded replies, and image carousels drop without error when the recipient falls back to SMS. Check capabilities first or accept that the plain text is all that's guaranteed to arrive.

Avoid known filtering triggers: public URL shorteners (bit.ly, tinyurl), ALL-CAPS runs, $$$, and sex/alcohol/firearms/tobacco content, which carriers filter regardless of campaign registration.

Quick start

{
  "tool": "preflight_message",
  "arguments": {
    "body": "Acme: thanks for signing up. Your order shipped. Reply STOP to unsubscribe.",
    "is_first_message_to_contact": true,
    "brand_name": "Acme",
    "to_number": "+14155552671"
  }
}