Developer Terms and Acceptable Use Policy

The API is offered to businesses and individuals 18 or older for lawful real-estate research and software integration. You must provide accurate account information and accept these Developer Terms on behalf of any entity you represent. One organization per account; keys may be shared only within your organization and with your own software. You are responsible for all use under your keys, including use by your employees, contractors and end users.

API responses are computed research derived from public county assessor records, third-party market aggregates, and deterministic calculators implementing published Washington rules. Responses are estimates, may be incomplete or out of date, and are not appraisals or opinions of value, and not legal, tax, lending, insurance or investment advice.

No response on this API surface is generated by a language model. The calculation tools are deterministic for the supplied inputs and applicable rule version. Data lookups may change as source records are updated. That is a property of the current surface, not a promise about every future endpoint — if a model-synthesized response is ever offered, it will be labelled as such in the response itself and in the changelog before you can call it.

In seller workflows, an omitted payoff or seller credit is unknown, while an explicit zero means none. Preserve the proceeds basis, known-value flags and comparison limitations in the response. A null scenario difference is not zero. Offer differences calculated before an unknown shared payoff do not establish final seller cash.

You must independently verify factual assertions before relying on them, and must present the response disclaimers and attributions to any person to whom you show the output. SENTINEL is not affiliated with or endorsed by NWMLS, the Washington Department of Revenue, any county, Redfin, or any data provider. Form defaults, tax tables and county extracts change; confirm current values with your broker or advisor.

You may:

1. query the API for individual property addresses, market areas and calculations;
2. display, store and analyze responses inside your own application or workflow;
3. create derivative analyses, reports and visualizations that incorporate responses, provided the attributions required by Section 5 are preserved.

You may not, and may not permit any third party to:

1. Build or sell lists of people. Compile, enrich or sell lists of individuals, owners, occupants or households from responses — alone or combined with other data — or identify or contact any person for marketing or solicitation. You may not append owner identity, phone, email or LLC-member data (including by skip tracing) to responses for solicitation.
2. Reconstruct the datasets. Enumerate, crawl, paginate or systematically query the API to reconstruct a parcel, sales or market database; export data in bulk; or retain raw sourced data fields (county records, market aggregates) longer than 30 days, except for addresses you continue to research. Computed outputs — REET, net sheets, deadlines — are yours to retain without limit, because they are math, not data.
3. Resell the raw feed. Redistribute, sublicense or sell raw responses, or offer a service whose principal value is access to SENTINEL data rather than what you built with it.
4. Discriminate. Use responses to make, support or target decisions or communications on the basis of race, color, religion, creed, national origin, sex, sexual orientation, gender identity, marital status, familial status, age, disability, veteran or military status, use of a guide or service animal, or any class protected under the Fair Housing Act (42 U.S.C. § 3601 et seq.) or RCW 49.60 — or to steer, exclude, or characterize neighborhoods or people by such classes, including by proxy.
5. Make consequential automated decisions. Use responses as an automated or sole basis for tenant screening, lease eligibility, consumer mortgage or credit underwriting, insurance eligibility or employment decisions, or in any consumer-report context under the Fair Credit Reporting Act.
6. Target distress. Identify, label or market to people on the basis of bereavement, probate, divorce, illness, foreclosure, tax delinquency or similar circumstances, or attempt to infer or reconstruct SENTINEL's suppressed signals (Section 7).
7. Send unlawful outreach. Use responses in calls, texts, emails or mail that violate the TCPA (47 U.S.C. § 227), CAN-SPAM, RCW 19.190, RCW 19.86, the National Do-Not-Call Registry, or applicable state law. SENTINEL sends no communications on your behalf.
8. Misrepresent the output. Represent responses as an appraisal, as MLS or NWMLS data, or as a county, NWMLS or government product; use any county's name, seal or logo to suggest endorsement; or remove or alter attributions, disclaimers, assumption fields or freshness fields. Source attribution must remain attached to displayed data.
9. Abuse the keys. Share keys outside your organization, expose a key in client-side code, evade rate limits or quotas, probe or reverse-engineer the service, or use responses to train machine-learning models without written permission.

Every response includes an attributions array. When you display or redistribute any part of a response you must reproduce each entry marked required: true in a location reasonably associated with the data, and state that factual assertions should be independently verified.

Two county lines and one market line are currently marked required and must be reproduced verbatim where their data appears:

• Pierce County
  “Pierce County does not warrant the Data in any way; these restrictions apply to any transferee, vendee or end user. Not a product of Pierce County.”
• Whatcom County
  “Data provided by permission of Whatcom County”
• Market aggregates
  “Data provided by Redfin, a national real estate brokerage.”

King County and Snohomish County source lines, and the NWMLS non-affiliation line, are supplied on every relevant response and should be carried through as well. Read required from the response rather than hard-coding this list — it changes when an upstream's terms change.

If you offer software or services incorporating responses, you must:

1. bind each end user to terms at least as protective as Sections 2, 4 and 5;
2. display “Powered by SENTINEL”;
3. keep keys server-side;
4. offer end users no capability prohibited by Section 4, including area enumeration or list export;
5. on request, describe your product and provide your end-user terms.

SENTINEL may suspend keys used by non-compliant products.

SENTINEL applies quarantine windows to certain public-record signals inside its agent application as an ethical floor. Those signals are not available through the API — there is no signals, lead, distress, court, probate, delinquency or foreclosure endpoint on this surface. No plan, add-on, fee, addendum or contractual term will make them available or shorten the windows. Attempting to reconstruct them is a material breach.

Owner and taxpayer names, mailing addresses, owner-status classification and equity estimates are not included in this version of the API, consistent with RCW 42.56.070(8) and the counties' own download terms. Nothing in these terms, and no fee, obliges SENTINEL to provide them.

King County, Pierce County, Snohomish County, Whatcom County and Redfin Corporation are intended third-party beneficiaries of Sections 4 and 5. If a provider changes or withdraws its terms, or objects to a use, SENTINEL may modify, restrict or remove affected fields or endpoints on notice — a changelog entry and, where practical, 30 days — without liability. Listing status, price and related fields are returned only for a matched licensed listing already on file. Null means no licensed listing on file, not that a property is not for sale. Listing links, photos and portal automated valuations are not returned. Known portal backfills of building attributes are omitted, and current listing overrides are replaced with cached property values. Historical cached attributes may include earlier enrichment and have not been independently verified field by field against county records. Source attribution does not establish that every field came from the named county. Preserve the response's provenance status and note when presenting these attributes.

The keyless calculators are free and rate-limited per IP. A free key includes 25 served answers for the lifetime of the account — not per month, not per key. Paid plans are subject to a ceiling of 2,000 served answers per account per rolling 24 hours, shared across every key on the account, together with the published burst rate limits.

Requests rejected for authentication, plan, validation, not-found or quota reasons are not billed and do not count against your allowance, and neither does the whoami probe.

Existing paid accounts retain their applicable API allowance. The optional $250 integration pilot runs for 30 days for one developer account with up to five integration keys, and includes setup help for one agreed workflow. It is a one-time payment with no automatic renewal. Checkout is available when configured; otherwise fit, access and payment are arranged directly before the pilot begins. Published per-account limits apply. Prices and quotas may change on 30 days' notice. Applicable sales tax is added at checkout or on the invoice.

The API is provided “as is”, without warranty of any kind, express or implied, including merchantability, fitness for a particular purpose, accuracy, completeness or non-infringement. No uptime, latency, accuracy or match-rate figure is promised, published or measured, and no service-level agreement applies to any self-serve plan. Data providers disclaim all warranties, assume no liability, and will not defend or indemnify you.

You will indemnify SENTINEL and its data providers against claims arising from your misuse of the API, your outreach, discrimination claims, and claims by your end users. SENTINEL's aggregate liability is capped at the fees you paid in the prior 12 months or $100, whichever is greater.

SENTINEL may monitor query patterns — address density per ZIP, sequential enumeration, unusual key sharing — and may throttle, suspend or terminate keys and refuse refunds on a reasonable belief of a Section 4 violation. You will cooperate with reasonable inquiries about your use.

Material changes are published here with a new version number and effective date, and noted in the API changelog. Continued use after the effective date is acceptance. If you do not accept a change, revoke your keys and stop calling the API.

Washington law governs, without regard to conflict-of-laws rules. Venue is King County, Washington. Disputes are resolved by AAA arbitration with a 30-day opt-out and a class-action waiver, mirroring SENTINEL Terms of Service §§14–15.

Questions about these terms, the integration pilot, or a use you are not sure is permitted: hello@sentineliq.net. Ask before you build it — the answer is usually yes, and it is cheaper than a suspended key.

Craig Headlee, founder — SENTINEL (sentineliq.net), a Washington real-estate data API, run as a sole proprietorship (DBA: Sentinel IQ).