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SMS Consent Model

How Metrognome obtains, records, and honors consent to text people. This page is the law of the land; the decision history lives in ADR-032 (decisions 22, 26, 32, 33). Ruled 2026-08-25.

The three tiers (CTIA)

US carriers enforce the CTIA Messaging Principles and Best Practices (May 2023). Exhibit II defines three content tiers, classified by who initiated and whether the message answers a request — not by whether a product is mentioned:

Tier CTIA definition (verbatim) Consent required
Conversational "If the Consumer initiates the conversation and the Non-Consumer simply responds, then no additional permission is expected." Implied — the inbound message is the consent
Informational "when a Consumer gives their phone number to a Non-Consumer and asks to be contacted in the future... the first text sent by the business fulfills the Consumer's request." Consent happens "when they give the Non-Consumer their mobile number." Express — "over text, on a form, on a website, or verbally"
Promotional "a message sent that contains a sales or marketing promotion." Express written — "sign a form, check a box online"

The checkbox is the promotional-tier mechanism. It is not required for informational texting, and CTIA's form-field guidance for informational is advisory ("can add a field"). TCPA's root is the FCC's 1992 order: "persons who knowingly release their phone numbers have in effect given their invitation or permission to be called at the number which they have given, absent instructions to the contrary."

Our purposes, senders, and gates

Purpose Sender What rides it Gate (canSend) on silence
transactional Toll-free (automated) Booking confirmations, access codes, receipts, payment notices, setup links Permitted — the customer's own action is the basis
customer_care CM numbers (Mixed campaign) 1:1 CM conversation: service, account, warm sales follow-up Blocked — requires a recorded opt-in
marketing Toll-free (registered, unused) Broadcast promotion (no program exists) Blocked — requires the customer's written opt-in

STOP is scoped per sender: a STOP to the toll-free ends transactional and marketing; a STOP to a CM number ends customer_care alone. An explicit opt-out blocks everywhere, and no automatic record (disclosed-purpose submission, phone verification, staff-typed number, backfill) ever reverses one; the audit event is still written. What can re-subscribe after an opt-out is the customer's own deliberate act, for that purpose alone: texting START to the number they stopped (restores what that sender carries, recorded as the keyword source), the promotional checkbox where one renders, or a signed-in member's own Promotional texts toggle in their account preferences (Aaron ruled 2026-08-25). Each is the customer's own act, recorded honestly as the source that carried it.

  1. Number given for a disclosed purpose (the workhorse). Wherever a phone number is collected — paid checkout, invitations, setup, and free forms like tour requests — the field carries a one-line disclosure naming who will text and why, plus "Reply STOP anytime." Submitting the number under that line is the informational consent, and the submit records sms/transactional + sms/customer_care opt-ins with the surface named. The request, not a purchase, is the basis, so free forms qualify. The phone may be required on purchase flows: it is required for the service itself (door codes, account security), not as a messaging gate.
  2. Given to a staffer in conversation. A customer telling staff their number while asking about a studio is CTIA's informational consent act verbatim. Staff creation flows record it automatically; the first text carries our identity and STOP.
  3. Inbound. Anyone who texts us first may be answered — the inbound is the consent for that conversation (not a standing subscription).
  4. The relationship backfill (ran 2026-08-25): every live customer with a phone holds a recorded customer_care opt-in under source: established_relationship.
  5. The promotional checkbox — the only checkbox the model permits on a lead-capture surface. The schemas and ledger accept it (smsMarketingConsent, signup_form), but no lead-capture surface currently renders it and no promotional SMS program exists; it gets built onto one if and when such a program does.
  6. The member's own preference-center toggle. A signed-in member's own act on the Promotional texts switch in their account preferences is express consent of the same grade as the checkbox (Aaron ruled 2026-08-25), recorded honestly as source: preference_center. Together with texting START, this is the re-subscribe path after a STOP or a mistaken opt-out, since staff cannot opt a customer in (Withdrawal, below) and signup_form only fires at signup.

Every basis lands in the consent ledger (consent_events + consent_states): contact point, purpose, action, source, surface, timestamp. The ledger is the defense we produce if ever asked — not the campaign registration, which stays as approved.

The CM classification rule

If you can name the request you're answering — their waitlist entry, their tour, their inquiry, their tenancy — it's not promotional. "The studio you wanted just opened, want to see it?" answers a request. What needs the written tier is what has no request behind it: coupon blasts, broadcast announcements, cold-list re-engagement, and texting a number that never reached out at all (never do this from our senders). One content trap, CTIA verbatim: "adding a call-to-action (e.g., a coupon code to an informational text) may place the message in the promotional category" — a discipline for automated sends.

Withdrawal

STOP always works and is honored immediately (carrier-enforced on our senders); the preference center offers per-purpose toggles. A customer who asks their CM to stop texting is told to reply STOP, which is instant and lands in the ledger through the carrier webhook; there is deliberately no staff-side withdrawal control (a staffer cannot opt a customer out any more than in). A customer's own opt-out can only be reversed by the customer's own act.

Sources