MLS Data vs. Public Listing Aggregators: What Actually Powers a Comp Report
"Automated comps" can mean very different things depending on where the underlying data actually comes from.
When a tool promises automated comparable sales, the reasonable follow-up question is: comparable to what, sourced from where? Two tools can both call themselves "automated comps software" while pulling from meaningfully different places — and that distinction affects how much weight the output deserves in a pricing conversation.
What MLS data actually is
Multiple Listing Service data is the closed system real estate agents and brokers use to share listing and sale information within a local market, maintained under agreements between brokerages and the regional MLS. It's generally the most complete and timely source for a given market, but access requires MLS membership or an approved data-sharing agreement — it isn't something any outside tool can simply connect to without going through that process.
What public listing aggregators are
Aggregators compile publicly visible listing data from consumer-facing real estate sites — the kind of listings anyone can browse without an MLS login. This data can be useful and genuinely comparable, but it's a different population than the closed MLS feed: it reflects active public listings rather than the full record of closed sales an MLS maintains, and coverage can vary by market and by how recently a listing was updated.
Why the distinction matters for pricing accuracy
Neither source is inherently "wrong" — but presenting aggregator-sourced data as if it were MLS data misrepresents its completeness and recency. A defensible comp report discloses which kind of source backs each section, so an agent (and their client) knows exactly how much confidence to place in a given number. That's a deliberate design choice, not an afterthought — a report should never blur the two.
What this means in practice
It means asking any comp tool — including this one — a direct question: is this MLS data, or is it aggregated from public listings? The honest answer shapes how a number should be used. A tool that's upfront about the distinction, and that labels sample or placeholder data as such rather than dressing it up as a live valuation, is doing the more defensible thing even if the underlying data source isn't the most prestigious-sounding option. See the full breakdown of what powers a CompsAgent report for exactly this kind of disclosure.
None of this changes the economics of getting a report built quickly — reports start at $79, with no subscription either way. What it should change is how much scrutiny you apply to any tool's marketing claims about "automated comps."
If the accuracy question interests you, it's worth reading about why the cost of getting tooling wrong compounds over time — inaccurate comps don't just cost a single deal, they cost trust.