Every contact-data vendor's homepage says roughly the same thing: verified emails, real-time data, huge database. None of that tells you whether it'll actually work for your list. Here's what to check before you commit, in the order it usually matters.
Coverage for your specific market, not their biggest number
A vendor advertising hundreds of millions of contacts can still be thin exactly where you sell. If you target mid-market manufacturing companies in the Midwest, or SaaS companies in a specific EU country, ask for a sample pull filtered to that segment — not the aggregate database size. A smaller, denser database in your niche beats a bigger one that's mostly noise for you.
Run your own accuracy test before you buy
Don't take a bounce-rate claim at face value. Pull a sample list — ideally contacts you can independently verify, like people at your own company or partners — and check it yourself. Most vendors will let you test a batch before a full commitment. If they won't, that's information too.
Understand what you're actually being billed for
This is the part people skip and regret later. Credit-based pricing means the sticker price on the landing page isn't your real cost — your real cost depends on your mix of cheap lookups (email search) versus expensive ones (phone numbers, which usually cost more credits). Before comparing two vendors' plans, map your expected monthly usage to each one's actual credit costs per operation, not just the plan price. Flat-rate pricing removes this step but trades it for a different constraint — usually a request-rate cap instead of a spending cap. Neither structure is objectively better; they suit different usage patterns.
Ask what happens when a record is missing or wrong
No database is complete. What matters is what the vendor does about it: do you get a refund or credit back for a bad email, or do you just eat the cost? Is there a live enrichment fallback when the static database doesn't have someone, or do you hit a dead end? This distinction — a static database versus a database with a live lookup behind it — matters more for coverage than any single accuracy stat.
Check where the data actually comes from
Ask directly: is this a proprietary database the vendor built, licensed data from third parties, scraped and inferred data, or some blend? Vendors vary widely here and it affects both accuracy and compliance posture. A vendor that can't or won't answer this clearly is worth being cautious about.
Confirm the compliance basics apply to your data
If you're prospecting into the EU or UK, ask how the vendor handles GDPR — what their lawful basis is for holding B2B contact data, and how they process opt-out and deletion requests. This isn't optional due diligence; it's the kind of thing that shows up in a partner or customer's security review later.
Test the integration path, not just the search UI
If your workflow lives in a CRM, a sequencer, or a script, check whether the vendor has an actual API (and ideally a documented one you can read before signing up) rather than only a web app you'd have to work around. A clean REST API with a rate limit you can plan around tends to matter more day-to-day than a slightly larger raw contact count.
None of this is specific to any one vendor — it's the same checklist we'd want someone running against us. Fyonta's docs are public if you want to see exactly what the API looks like before you sign up for anything.