MLS listing data is accessible via API through several paths, each with different access requirements, coverage, and cost. Understanding the options determines which approach fits your use case and market.
Direct MLS Board API Access
Most regional MLS organizations provide API access through the RESO (Real Estate Standards Organization) Web API standard. Access requires either an active real estate license in the relevant market or a data licensing agreement with the MLS board. Direct board access provides the freshest data — typically updated within hours of listing changes — and the most complete field coverage including agent contact information. The limitation is geographic: a direct agreement with the Houston Association of Realtors covers Houston but not Dallas, requiring separate agreements for each market.
Third-Party MLS Data Aggregators
Aggregators like Cotality Trestle, Bridge Interactive, and Real Estate Webmasters license MLS data from multiple boards and provide a unified API that covers many markets under one agreement. Coverage varies by provider — some cover 600 or more MLSs, others focus on major metros. The tradeoff is cost (aggregator agreements typically run $200 to $2,000 per month depending on data volume) versus the convenience of one contract and one API for multi-market coverage.
Public Data Sources
For markets where direct or aggregator access isn't feasible, some investors use publicly available listing data from sites that expose listing information without the full RESO field set. This approach lacks agent contact information directly and requires a separate enrichment step. The full MLS-to-outreach pipeline using API data is demonstrated at omnionlinestrategies.com/real-estate-agent-outreach-machine.