# Key concepts

Company, signal, lead, qualified lead, and the credits each one spends.

Five words cover the API. The same words are what you say to an assistant.

## Company

A **company** is the employer, looked up by name (`lookup_company`, `GET /companies/lookup`, free) or enriched with firmographics (`POST /company/enrich`, **1 credit** when a company is found). You start here when you already know who you sell to.

## Signal

A **signal** is a buying moment: a funding round, a new role, a post, a technology, an event, people reacting to a company page. `find_leads` and `POST /searches` run one. A monitor or a watch keeps listening after the first search. The company did the thing, or a person did. The wording in the result keeps those apart.

## Lead

A **lead** is a person returned for a role, a seniority, a department, or a signal. `company_leads` and `POST /leads` charge **5 credits** per person. Those rows use `per_` ids. They are people at a company you named, not a qualified signal lead.

## Qualified lead

A **qualified lead** is a person a screened search kept because they fit the buyer profile. `find_leads` charges **20 credits** for an exact fit and **5 credits** for someone just outside. The id starts with `lead_`. `explain_lead` (`GET /leads/{lead_id}`) is free and is the "why this lead" step: fit, why now, and the evidence. It does not accept a `per_` id.

## Credits

**Credits** are the shared balance for the app, MCP and REST. You pay for a row that comes back. A preview (`preview_cost`, and the `/preview` routes) is free and returns the worst case, including `max_credits`. The table is [Credits & costs](/docs/api/credits-and-limits).