Trestle’s Phone Activity Score is a 0-100 value that indicates whether a phone number is connected and actively used, not just whether it’s syntactically valid. Scores of 70+ indicate consistent activity and high contactability; scores of 30 or below indicate disconnection or inactivity. Phone Activity Score is available in Phone Validation API, Real Contact API, and Decision Console and is built from carrier signals, line type metadata, and Trestle’s proprietary network observed over the last 12 months. It complements our phone validity, line type, and carrier attributes.
What is a Phone Activity Score? #
Phone Activity Score is a 0–100 rating returned by our Phone Validation API, Real Contact API, and Decision Console that indicates how active a phone number has been over the last 12 months. Unlike phone validity, which only confirms whether a number’s syntax and carrier assignment are correct, Phone Activity Score tells you whether the number is actually in use.
The score is built from a machine-learning model that aggregates carrier signals, call connectivity data, line type behavior, HLR lookups (where available, internationally), and signals from Trestle’s own verified call network. It’s available globally, though coverage depth varies by country. You’ll see it in API responses as the activity_score field.
How do I read Phone Activity Score? #
The score ranges from 0 to 100. Here’s what the bands mean:
| Score | What it means |
| 70+ | High confidence the phone is connected, assigned to a subscriber, and has shown consistent activity. Prioritize these for outreach. |
| 50 | Insufficient signals to determine connection status with confidence. Treat as uncertain — verify through a secondary channel before high-cost outreach. |
| 30 or below | High confidence the phone is disconnected, or no one is answering when dialed. Strong candidates for suppression. |
Trestle’s recommended baseline filtering rules:
- Prioritize scores of 70 or above
- Suppress scores of 30 or below
Different teams set thresholds differently based on tolerance for false positives. Some may accept 50+ for low-cost channels like email, while outbound dial campaigns may set the bar at 70+.
How is Trestle’s Phone Activity Score Calculated? #
Phone Activity Score is the output of a machine-learning model that combines external and internal signals to produce a score that updates as new data is observed.
External signals include:
- Call connectivity data from carriers and cross-carrier network enablers
- Phone metadata changes (carrier, line type, prepaid status)
- Disconnect signals from carriers
- Public records and metadata attributes
Internal signals include:
- The most recent date the number was seen in a verified call on Trestle’s network
- The frequency of verified calls involving the number within a given time window
Refresh cadence: When a phone changes carriers, that information is reflected in Trestle’s data within 15 minutes, and the new signal feeds the score in near real-time.
Evaluation window: Trestle evaluates phones over the last 12 months of data. Scores don’t jump from 0 to 100 (or vice versa) overnight, except in cases where a carrier provides a clear disconnect signal. The score weights consistency over time.
Line type also factors into the score’s behavior. For example, a non-fixed VoIP number without an identified owner gets weighted more heavily toward inactivity than a mobile number with a known subscriber, because non-fixed VoIP numbers are commonly used as throwaway numbers and carry higher inactivity risk.
Phone validity vs. Phone Activity Score: what’s the difference? #
These two signals are often confused. They answer different questions:
| Phone Validity (is_valid) | Phone Activity Score | |
| What it answers | Is this number structurally valid and assigned to a carrier? | Is this number actually being used? |
| Output | Boolean (true / false) | Numeric score (0–100) |
| Best for | Filtering nonsense input, format checks at point of entry | Prioritizing reachable contacts, suppressing inactive numbers |
| Limitation | Says nothing about whether the number is in service or will be answered | Requires recent activity signals; brand-new numbers may show low scores until signals accumulate |
A number can be valid but inactive (i.e., someone canceled service but the number hasn’t yet been reassigned) — or technically valid but consistently unanswered. That’s the gap Phone Activity Score fills.
Common combined rules:
- Lead prioritization: is_valid = true && activity_score >= 70
- SMS campaigns: is_valid = true && activity_score > 30 && line_type = “Mobile”
- Fraud screening for sign-ups: is_valid = true && line_type != “NonFixedVOIP” && activity_score > 30
Phone Activity Score vs. HLR Lookups #
HLR (Home Location Register) lookups query a mobile carrier’s network in real-time over the SS7 signaling system to confirm whether a number is currently registered to a subscriber. They’re a useful technical check, but they answer a narrower question than Phone Activity Score.
| HLR Lookup | Phone Activity Score | |
| What it tells you | Is this mobile number currently registered on a carrier network? | How recently and consistently has this number shown real usage? |
| Coverage | Mobile numbers; limited insight for VoIP/landline | All phone types (mobile, landline, fixed and non-fixed VoIP, etc.) |
| Timeframe | Point-in-time snapshot | 12-month behavioral window |
| Detects “valid but unused”? | No. A registered but unused number passes HLR | Yes. Low Phone Activity Score flags inactivity even if registered. |
| Detects throwaway/disposable VoIP? | Limited | Yes. Line type weighting flags non-fixed VoIP risk. |
In short: HLR confirms registration status. PAS measures real-world activity. The two answer different questions, and PAS is generally more useful when the goal is to predict whether a number will actually answer.
How accurate is Trestle’s Phone Activity Score? #
For Phone Activity Score, Trestle measures accuracy by false-positive rate, or the rate at which a number is scored as active when it is not. That false-positive rate is below 1% globally, with 99%+ coverage.
For reference, the rest of Trestle’s Phone Validation API accuracy figures:
| Attribute | Coverage | Accuracy |
| Phone Validity | 100% | 100% |
| Phone Carrier | 99+% | 99+% |
| Line Type | 99+% | 99+% |
| Phone Activity Score | 99+% | False positives below 1% |
It’s important to note that Phone Activity Score coverage varies by country. Trestle classifies country-level activity coverage as:
- High coverage: Activity signals available for more than 70% of phone numbers in that country
- Medium coverage: 30–70% of numbers
- Low coverage: Fewer than 30% of numbers
High-coverage countries include the UK, Germany, Australia, Japan, Saudi Arabia, Norway, Sweden, Switzerland, the Netherlands, Poland, Turkey, the UAE, Thailand, Malaysia, Hong Kong, Taiwan, Nigeria, Ireland, and others. Some major markets such as India, China, Brazil, France, and New Zealand fall into Low or Medium tiers, so Phone Activity Score in those countries should be treated as a useful but partial signal.
When should you re-check Phone Activity Score? #
Phone numbers decay. Industry estimates and Trestle’s own observations put annual contact data decay at roughly 18–25%, meaning up to a quarter of your phone records could potentially become stale or inaccurate in a year.
Trestle’s general guidance:
- Validate at point of entry for new leads and sign-ups
- Re-validate existing databases at least quarterly, more often for large or high-priority lists
- Pair with Litigator Checks when used for outbound dialing. The FCC’s Reassigned Numbers Database tracks numbers that have been permanently disconnected and possibly reassigned, and calling a reassigned number can create TCPA liability under 47 U.S.C. § 227, which provides for $500 per violation and treble damages for willful violations.
Common Use Cases for Phone Activity Score #
Lead Prioritization #
Route leads with high Phone Activity Scores (70+) to phone-first outreach. This is the foundation of Trestle’s A-F Contact Grade in Real Contact API, which combines Phone Activity Score with line type and identity match into a single decision-ready field.
Lead Filtering #
Filter out scores at or below 30 before they reach a dialer. This reduces wasted agent minutes, preserves contact rate metrics, and helps keep your outbound numbers from being flagged as spam.
Fraud and Signup Risk #
Combine low Phone Activity Score numbers with a non-fixed VoIP line type to flag throwaway numbers used in promo abuse and synthetic identity fraud. Add friction (step-up verification) at sign-up rather than auto-blocking.
CRM and Database Hygiene #
Re-score your existing contact base on a regular cadence to remove decayed records and surface contacts worth re-engaging.
SMS Deliverability #
Layer Phone Activity Score with line type filtering (line_type = “Mobile”) and validity checks to focus messages on numbers most likely to receive and respond.
Surveys and Research #
Independent peer-reviewed research has found that recent-activity flags improve cellphone sampling efficiency. Phone Activity Score is the same kind of signal applied to commercial outreach.
What Phone Activity Score Doesn’t Do #
To be transparent about scope:
- Phone Activity Score is not an identity check. It indicates whether a number is in use, not who owns it. Use Real Contact API for phone-to-name matching or Reverse Phone and Caller Identification APIs to enrich caller information.
- Phone Activity Score is not a TCPA litigator check. A high Phone Activity Score does not mean a number is safe to call. For enhanced TCPA compliance measures, layer in our Litigator Checks Add-on.
- Phone Activity Score coverage varies by country. Trestle returns Phone Activity Score globally, but signal depth differs by market. In low-coverage countries, Phone Activity Score is still returned and accurate when it’s confident, but a larger share of numbers may not have enough signal to score reliably.
- Phone Activity Score may be lower for legitimately inconsistent users. Someone who uses a Google Voice number only for occasional 2FA codes may show a low score, since it reflects observable activity, not intent.
Which Trestle APIs return Phone Activity Score? #
| API | Includes Phone Activity Score? | Notes |
| Phone Validation API | Yes | Phone Activity Score is a core field alongside is_valid, line_type, carrier, and is_prepaid. |
| Real Contact API | Yes | Phone Activity Score is included in the response, and influences the A-F Contact Grade. |
| Reverse Phone API | No | Returns ownership and demographic data, not activity scoring. |
| Caller Identification API | No | Returns caller identity data, not activity scoring. |
How do I get started with Phone Activity Score? #
You can test Phone Activity Score using Trestle’s free trial, which includes 14 days of access to both Phone Validation API and Real Contact API. No credit card required.
To set up:
- Sign up through the Developer Portal and grab your API key.
- Make a test call to Phone Validation API. The activity_score field is returned by default.
- Set your filtering thresholds based on the use case (70+ for high-priority outreach, 30 or below for suppression, or your own bands).
- Re-validate on a cadence. For most teams, that would be quarterly at minimum.
Frequently Asked Questions #
Is Phone Activity Score available for international phone numbers?
Yes. Phone Activity Score is returned globally, with 99+% coverage and a false-positive rate below 1%. Internationally, the score incorporates HLR lookups where available alongside other carrier and network signals. Coverage depth varies by country.
Does a Phone Activity Score of 50 mean the number is partially active?
No. A score of 50 means Trestle does not have enough signals to predict the number’s status with confidence. It’s a “treat with caution” indicator, not a midpoint of activity.
How quickly does the score update after a number is disconnected?
When a carrier provides a disconnect signal, the score reflects it in near real-time. For numbers that gradually go inactive without a carrier signal, the score declines over the course of weeks as the 12-month window registers the absence of activity.
What’s the difference between Phone Activity Score and Contact Grade?
Phone Activity Score is one signal. Contact Grade (A-F, returned by Real Contact API) combines Phone Activity Score with line type, identity match, and risk signals into a single decision-ready letter grade.