Spark API vs ATTOM Property API for AI agents
FBS's Spark API and RESO Web API give authorized applications access to MLS data on the Flexmls/Spark platform. ATTOM Property API is a REST API for US property records: ownership, sales history, valuations (AVM and rental AVM), mortgages, schools, crime and neighborhood data.
The short answer
- Spark API: Apps built for agents, brokers or MLSs that use Flexmls, where the MLS member authorizes access.
- ATTOM Property API: Deep public-record and valuation data on any US property, rather than finding homes currently on the market.
Side by side
| Spark API | ATTOM Property API | |
|---|---|---|
| Searches | MLS listings (and, for VOW apps, sold data) from participating MLSs, within the roles each MLS grants. | Properties by address, parcel number, ATTOM ID or latitude/longitude; the docs describe last sales, sales history and valuations, not active for-sale or rental listings. |
| Returns | MLS listing records in Spark or RESO Web API format. | JSON or XML property records with characteristics, ownership, sale history, AVM values and area data. |
| Before the first call | A free developer account, then an MLS data plan or an MLS member who authorizes your app. | A trial sign-up to receive an API key; production plans through ATTOM. |
| Free | Developer account sign-up is free. | 30-day free trial with an API key. |
| Paid | $50 a month for each MLS you access, once you have data from your first MLS (MLS data plans may set their own terms). | Not stated on its pages |
| Acting on a result | Not stated on its pages | Nothing: no agent, landlord or listing contact fields are described. |
| Limits on keeping or showing results | No storing MLS content except temporary caching for performance, unless your key permits replication; MLS display rules and license terms apply. | Use of data is governed by a separate license agreement that is not published on the site. |
| Coverage | Participating MLSs on the FBS platform; no list or count on its pages. | US, 160+ million properties. |
| MCP server | No official server listed | ATTOM MCP Server (access arranged through ATTOM): https://www.attomdata.com/solutions/delivery/mcp-server/ |
Where Openpath fits
Openpath has no homes listed yet. Owners and landlords can list a home for rent or sale on Openpath today, free, and agents will find it through the same search as jobs and businesses. Get listed.
Questions people ask
What do I need before I can use Spark API?
A free developer account, then an MLS data plan or an MLS member who authorizes your app.
Is Spark API free?
Developer account sign-up is free.
What do I need before I can use ATTOM Property API?
A trial sign-up to receive an API key; production plans through ATTOM.
Is ATTOM Property API free?
30-day free trial with an API key.
Sources
Every line about another company comes from its own pages. Prices and terms change, so check the source before you rely on one.
Spark API, read on October 15, 2026:
- sparkplatform.com/docs/overview/api: “The Spark API allows authorized MLS members to request data through developer applications”
- sparkplatform.com/docs/overview/api: “When IDX applications are purchased, the MLS member must authorize that application to access their data.”
- sparkplatform.com/docs/overview/faq: “It’s free to sign up for a Spark API developer account.”
- sparkplatform.com/docs/overview/faq: “Once you have access to data from your first MLS, API access costs $50/mo for each MLS you can access.”
- sparkplatform.com/docs/terms_of_use/developer_agreement_and_terms_of_use: “except for temporary caching purposes necessary for performance enhancement”
- sparkplatform.com/docs/terms_of_use/developer_agreement_and_terms_of_use: “Compliance with MLS Rules and License Terms regarding MLS Content”
ATTOM Property API, read on October 15, 2026:
- attomdata.com/solutions/property-data-api: “Sign up for a free 30-day trial to receive an API key and explore ATTOM’s extensive property data”
- attomdata.com/solutions/property-data-api: “Covering 160+ million U.S. properties and 99% of the U.S. population”
- attomdata.com/solutions/property-data-api: “ownership information, lat/long, square footage, loan types, sales history, sales comps, crime, schools and more”
- api.developer.attomdata.com/docs: “return information pertaining to the most recent sale of a property or list of properties”
- attomdata.com/solutions/property-data-api: “The ATTOM MCP Server provides AI-native access to ATTOM Intelligence through the Model Context Protocol (MCP).”
- attomdata.com/solutions/delivery/mcp-server/how-it-works: “Access is governed, permissioned, and centrally managed”
- attomdata.com/terms-of-use: “subject to the terms of a separate license agreement”