Contact enrichment APIs,
explained.
A contact enrichment API takes an identifier you already have for a person and returns the contact information you don't: verified emails, phone numbers, social profiles. This guide covers how they work, what separates them, and how to evaluate one. Written by someone who builds one, with the bias that implies stated where it matters.
The shape of the thing
Every contact enrichment API reduces to the same contract: identifier in, contact record out. The differences that matter hide in three places: which identifiers it accepts, what the record contains, and how you pay when the lookup fails. Here's the contract in its entirety:
curl "https://peopledb.co/api/v1/people?linkedin_public_identifier=dhh" \
-H "Authorization: Bearer $TOKEN"
// ←
{
"linkedin_public_identifier": "dhh",
"github_login": "dhh",
"email_addresses": ["david@hey.com", "dhh@basecamp.com"],
"personal_email_addresses": ["david@hey.com"],
"work_email_addresses": ["dhh@basecamp.com"],
"phone_numbers": []
}Inputs: what you can start from
The identifier you hold determines which tools can help you at all, so start your evaluation here, not at the pricing page. The market splits roughly like this:
| You have | The lookup this implies | Typical tool shape |
|---|---|---|
| A company domain | Which emails exist at this company? | Domain-first email finders |
| A name + company | What's this person's work email? | Prospecting platforms, waterfalls |
| An email address | Who is this, and is it deliverable? | Reverse lookup + verification |
| A LinkedIn profile | How do I reach this person? | Extensions, or person-first APIs |
| A GitHub login or ID | How do I reach this developer? | Rare; PeopleDB's specialty |
Direct providers vs. waterfalls
A direct provider maintains its own index and answers from it. A waterfall provider holds little data itself; it relays each lookup through several underlying vendors and returns the best hit, usually charging only for verified results. The trade is clean: waterfalls buy you the market's combined match rate at the market's combined price, while direct providers are cheaper per lookup and faster, but bounded by their own coverage.
A rule of thumb: small, precious lists (hard-to-reach founders, candidate shortlists) justify waterfall economics. Steady programmatic volume favors going direct, then falling back to a waterfall only for the misses. Since a well-built direct lookup only charges on a hit, the blended cost of "direct first, waterfall for the remainder" is usually the best of both.
How to evaluate one before you commit
Where PeopleDB fits
PeopleDB is a direct, person-first enrichment API with a deliberately narrow contract: a LinkedIn or GitHub identifier in, verified emails (classified personal or work), phone numbers, and social handles out. Lookups are prepaid (15¢ down to 6¢ at volume), charged only when at least one email is returned, and credits never expire. There is no discovery, no platform, and no sales call; the docs and pricing are public and a new account starts with 10 free credits.
Where it isn't the answer: domain-first email finding, prospecting by filters, or company-level enrichment. We compared seven tools across those use cases honestly, including where each beats us, and keep head-to-head pages for ContactOut, Apollo, Hunter, and Clearbit.
If you'd rather see it than read about it, the LinkedIn lookup tool runs the same API from a form, and the engineering behind the data is documented on the blog: how GitHub lookups actually work and what email verification can and can't promise.