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linkedin_to_mobile_phone is the only phone endpoint in the API. It takes a LinkedIn profile and returns a carrier-verified mobile number with the date it was last verified.

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Mobile only, by design

Only mobile numbers are returned — no landlines, no VoIP. Every result is a real device, which is what makes the output usable for SMS and direct dial rather than a switchboard you have to navigate. The practical consequence: contacts whose only number is a desk line simply won’t return a result. A miss here isn’t a data gap so much as a filter working as intended.

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Batch up to 100 per call

The endpoint takes either a single URL or a batch: Batching is the single highest-leverage practice here. One call for 100 profiles instead of 100 calls cuts your request count by 99%, which matters because every request counts toward your rate limit regardless of whether it returns data.
For lists longer than 100, chunk into batches of 100 and pause briefly between them rather than firing everything at once. See Rate Limits for the per-plan ceilings.

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Budget external tokens first

Mobile phone lookups require external tokens, at a cost of 10 external tokens per returned result. This is a separate balance from your regular tokens, and it is the most expensive lookup in the API per result.
A 100-profile batch that resolves fully costs 1,000 external tokens. Plan runs against your balance before you start: get_account and get_billing are free and never cost tokens. Read external_token_balance before a large run so a job doesn’t stall halfway through. You’re only charged for results that come back — profiles with no mobile on file cost nothing.

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Qualify before you enrich

Because this is the priciest per-result lookup, it pays to narrow the list before calling it rather than after. Run your people search filters first and enrich only the contacts you’d actually call:
  1. search_people with seniority, department, and location filters
  2. Review results.total and tighten until the list is the size you intend to work
  3. Batch the resulting LinkedIn URLs into linkedin_to_mobile_phone, 100 at a time
Enriching a 5,000-row list “just in case” is how an external token balance disappears in one afternoon.

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Read the validation date

last_validated_at is the date the number was last confirmed active and in service.
Unlike email, MoltSets does not assign a risk score or confidence grade to phone numbers. The validation date is the signal — a number confirmed last week carries more confidence than one confirmed a year ago, and it’s your call how much weight to give it. See Understanding Phone Number Validation.
Set a staleness threshold that matches the channel. Cold calling a number verified 18 months ago wastes a dial; sending SMS to one wastes money and can generate complaints.

Phone Number Validation

What the validation date does and doesn’t tell you.

Rate Limits

Batching, backoff, and per-plan ceilings.