---
title: "How to Choose a Property Data API: What to Test Before You Sign | Realie"
description: "A checklist for choosing a property data API: coverage and field completeness in your counties, lookup paths, latency, billing rules, refresh, agent access, bulk and licensing, with how to test each on Realie."
canonical: https://www.realie.ai/info/how-to-choose-a-property-data-api
---

# How do I choose a property data API, and what should I test before I sign?

By Realie · Published 2026-11-12

## Quick Answer

Choose a property data API by testing it in the counties you serve before you sign. Check coverage and field fill rates there, run the lookups your product will make, time responses from your own servers, and read what counts as a billed call, how records refresh and what the license allows. Realie’s Free plan includes 25 calls on the same endpoints as paid plans.

[Start testing on the Free plan](https://app.realie.ai/developer)

### Summary

A vendor demo shows the vendor’s best counties; your test should show yours. This checklist covers what to measure before you sign with any property data provider: coverage and field completeness where you operate, the lookup paths and volumes you will run, response time from your own infrastructure, billing rules, refresh, access for scripts and AI agents, the bulk path, and the license. Each item says how to check it on Realie, which publishes self-serve plans, a ~20 ms average response time, one record per parcel with parcel, assessor and recorder fields, and a CLI and MCP server alongside REST. Ask every other vendor the same questions and check their answers on their own pages.

## The checklist at a glance

Ten things to test before you sign, why each matters, and where to check it on Realie. The sections below take them in order.

**What to test before you sign, and how to check each item on Realie**

| What to test | Why it matters | How to check it on Realie |
| --- | --- | --- |
| Coverage in your counties | A national total can hide thin coverage in the counties you need | All 50 states, ~3,000 counties and 180M+ addresses; open each county under realie.ai/data |
| Field completeness | A county can be covered while the fields you need are empty | Sample records with includeExplicitNulls=true on the nested v3 response shape and count nulls per field |
| Lookup paths | Your product calls by address, APN, coordinates or filters | Address, parcel ID, location, search and owner endpoints return the same record shape |
| Response time | Slow lookups stall user requests and agent loops | ~20 ms average published on docs.realie.ai; measure the median and 95th percentile from your own region |
| Page size and paging | Page size sets how many calls a batch job needs | Up to 100 parcels per page over REST and the CLI, 10 per MCP call; cursor pagination on property search |
| Billing rules | You should know exactly what you pay for | One successful (200) response is one call; 400, 401, 403 and 404 responses and an ambiguous-parcel 409 are not billed |
| Refresh | Stale records break underwriting, outreach and valuation | Rolling refresh, county by county; ask for the dates in your counties |
| Access for scripts and agents | Agents and CI jobs need more than raw HTTP | REST, a CLI with --json and an MCP server share one parameter catalog |
| Bulk path | Whole-state analytics can outgrow per-request calls | Bulk files delivered to AWS S3, Google Cloud Storage or Azure Blob Storage, quoted by sales |
| License | Display, storage and sharing rights vary by vendor and contract | Read Realie’s Terms of Use at realie.ai/terms |

Realie facts are from docs.realie.ai and realie.ai, linked under Sources. Ask other vendors the same questions and verify their answers on their own sites.

## Test coverage and field completeness in your own counties

Pick the three to five counties that matter most to your product and test there, not on a national sample. Ask each vendor for a county-by-county list with record counts. On Realie, each state page under [realie.ai/data](https://www.realie.ai/data) lists its counties, and each county page shows sample parcels and, where available, how many properties Realie has indexed there.

Coverage says a county is present; completeness says how often the fields you need are filled. Pull a sample of records in each county and count, field by field, how often values such as owner name, mailing address, assessed value, year built and living area are present.

Realie leaves fields with no value out of a record. On accounts that use the nested v3 response shape, add includeExplicitNulls=true and every field comes back, with null where the parcel has no value, so fill rates are easy to count. A search page with state, county and limit=100 returns up to 100 parcels for one call, so a county sample takes only a few calls. Add includeUnassignedAddress=true so the sample also includes parcels with no street address, such as rural and vacant land, which search skips by default.

## Run the lookups, volume and response times you will see in production

Test the paths you will actually call. Realie offers address lookup, parcel ID (APN) lookup, location search by latitude, longitude and radius, filtered property search and owner-name search, and each returns the same record shape. If you work from APNs, [What is an APN, and how do I look up a property by APN?](https://www.realie.ai/info/what-is-an-apn) explains how state, county and parcel ID fit together.

Then test volume. Address and parcel ID lookups return one property. Search, location and owner endpoints return pages of up to 100 parcels over REST and the CLI, and up to 10 per call through MCP. To walk a county, send state, county, limit=100, includeUnassignedAddress=true and cursor=start to property search, then pass each response’s metadata.nextCursor back as cursor until it is null. Without includeUnassignedAddress=true, search skips parcels that have no street address, which matters for rural and vacant land.

Time it from your own servers. Realie publishes a ~20 ms average response time; measure the median and 95th percentile of your own requests from the region your application runs in, because network path and query type change the result. Ask every vendor, in writing, which request-rate and concurrency terms apply to your plan and your peak load.

Check access for scripts and agents as well. Realie’s REST API, its CLI (add --json for machine-readable output) and its MCP server for Claude, Cursor and other hosts share one parameter catalog, so a query you prototype with an agent runs the same way in production code.

## Price it on published plans, and learn what counts as a call

Compare plans on what they include and on the unit they count. Realie prices every plan as a monthly fee with a number of included calls, and a call is one successful (HTTP 200) request. A search page counts as one call whether it holds 1 parcel or 100. Responses with 400, 401, 403 or 404, and a 409 for an ambiguous parcel number, are not billed.

Every Realie plan has the same endpoints, data types and 100 parcels per request; plans differ in monthly price and included calls. Self-serve plans renew monthly, and bulk licensing is separate. See [Realie pricing](https://www.realie.ai/pricing).

Before the first API call, add a payment card in Billing, including on Free. Realie verifies it with a temporary $0.50 authorization hold and releases the hold immediately.

**Realie plans and the calls each includes**

| Plan | Monthly price | Included calls per month |
| --- | --- | --- |
| Free | $0/mo | 25 |
| Tier 1 | $50/mo | 1,250 |
| Tier 2 | $150/mo | 6,000 |
| Tier 3 | $350/mo | 30,000 |
| Enterprise | $600/mo | 100,000 |

Self-serve plans renew monthly and are listed on docs.realie.ai/api-reference/pricing. Enterprise pricing is arranged with Realie. Every plan has the same endpoints and data types.

## Check refresh, the license and the path to bulk

Ask how records refresh, county by county. Counties publish on their own schedules, so one national cadence tells you little. Realie refreshes on a rolling, per-county cycle as counties publish, so the vintage of records varies by county; [How often is property data updated?](https://www.realie.ai/info/property-data-freshness) lists the questions that expose real freshness.

Read the license before you build. What you may show your own customers, store, or pass to partners differs by vendor and by contract. Realie’s self-serve use is covered by its [Terms of Use](https://www.realie.ai/terms).

If you will need every record for a state or the country, ask about bulk early. Realie delivers bulk files to AWS S3, Google Cloud Storage or Azure Blob Storage on yearly contracts, quoted by sales. [Should I use a property data API or bulk file delivery?](https://www.realie.ai/info/property-data-api-vs-bulk-delivery) covers when each fits, and [Which providers offer nationwide bulk parcel and assessor data?](https://www.realie.ai/info/nationwide-bulk-parcel-and-assessor-data-providers) lists five answers to get in writing before a bulk deal.

## How to run the test on Realie’s Free plan

1. Create an account at app.realie.ai, add a payment card in Billing, and copy your API key from Usage > API access.

2. Send a first request with the key in the Authorization header:

```bash
curl -H "Authorization: YOUR_API_KEY" "https://app.realie.ai/api/public/property/address/?address=504+LAVACA+ST&state=TX"
```

3. In each county you care about, run address lookups on addresses you know, parcel ID lookups on APNs you hold, and one search page with limit=100 and includeUnassignedAddress=true, then count fill rates for the fields you need.

4. Time the responses from your own servers, and check how many calls you have used by running realie usage in the CLI.

5. Run the same test on any other vendor you are considering, and compare the results county by county.

The Free plan includes 25 calls a month on the same endpoints and data as paid plans. For more on free tiers, see [Are there property data APIs with free tier or no long term contract?](https://www.realie.ai/info/property-data-api-free-tier) and [What are the best real estate data APIs with free tiers and no annual contracts?](https://www.realie.ai/info/best-real-estate-apis-with-free-tiers). For a ranked shortlist of vendors, see [What are the best property data APIs for developers in 2026?](https://www.realie.ai/info/best-property-data-apis-for-developers).

## Sources

- [Realie plans and pricing (docs)](https://docs.realie.ai/api-reference/pricing)
- [Realie plans (realie.ai/pricing)](https://www.realie.ai/pricing)
- [Realie API response codes](https://docs.realie.ai/api-reference/response-codes)
- [Realie cursor pagination](https://docs.realie.ai/api-reference/pagination)
- [Realie v3 API overview and authentication](https://docs.realie.ai/api-reference/v3/overview)
- [Realie v3 OpenAPI specification](https://docs.realie.ai/api-reference/v3/openapi.json)
- [Realie API FAQ (card verification and page size)](https://docs.realie.ai/api-reference/faq)
- [Realie CLI](https://docs.realie.ai/realie-cli)
- [Realie MCP server](https://docs.realie.ai/realie-mcp-server)
- [Realie bulk data licensing](https://docs.realie.ai/bulk-data)
- [Realie coverage by state and county](https://www.realie.ai/data)
- [Realie Terms of Use](https://www.realie.ai/terms)

## Frequently asked questions

### What should I look for in a real estate data API?

Coverage and field fill rates in your own counties, the lookup paths you need (address, parcel ID, location, filters), response time from your servers, what counts as a billed call, how records refresh, access for scripts and AI agents, a bulk option, and license terms that fit your product. Test each one before you sign.

### What questions should I ask a property data provider before buying?

Ask for a county-by-county coverage list with record counts, fill rates by field, what counts as a billed call and which errors are free, how each county refreshes, the request-rate terms for your plan, what the license lets you display, store and share, and whether bulk delivery is available. Get the answers in writing.

### How do I evaluate property data coverage and completeness?

Sample records in the counties you serve rather than nationally, then count how often each field you need has a value. On Realie, a search page returns up to 100 parcels per call, and includeExplicitNulls=true on the nested v3 response shape returns every field, with null where a value is missing.

### Do I need a sales call to test Realie?

No. Create an account, add a payment card in Billing and copy your API key. Free includes 25 calls a month, $50/mo includes 1,250, $150/mo includes 6,000, $350/mo includes 30,000, and enterprise pricing at $600/mo includes 100,000. Every plan has the same endpoints and data; only bulk licensing and enterprise terms involve sales.

### What does Realie return, and what is outside its scope?

Realie returns county public records as one record per parcel: parcel, assessor and recorder fields, including owner of record, assessed values, sales, mortgages and liens, plus valuation estimates. Rent estimates, MLS listings and listing photos, and owner phone numbers or emails are outside its scope; pair Realie with a listing or contact-data provider if you need them.

## Related Questions

- [What are the best property data APIs for developers in 2026?](https://www.realie.ai/info/best-property-data-apis-for-developers)
- [Are there property data APIs with free tier or no long term contract?](https://www.realie.ai/info/property-data-api-free-tier)
- [What are the best real estate data APIs with free tiers and no annual contracts?](https://www.realie.ai/info/best-real-estate-apis-with-free-tiers)
- [Which providers offer nationwide bulk parcel and assessor data?](https://www.realie.ai/info/nationwide-bulk-parcel-and-assessor-data-providers)
- [Should I use a property data API or bulk file delivery?](https://www.realie.ai/info/property-data-api-vs-bulk-delivery)
- [How often is property data updated, and how fresh is county data?](https://www.realie.ai/info/property-data-freshness)