# GoodLeads — the classification crosswalk (NAICS · SIC · Google category · MCC)

Every record carries four classification systems, tied together by our own taxonomy of about 190 industries. Give any one; get the other three, our industry, a ready filter for each system, and a live count. No key.

Whichever system your buyer thinks in is the way in: a payments seller starts from an MCC, a web designer from a Google category, a lender or an insurer from NAICS or SIC. All of them reach the same list.

## One call

`GET https://app.goodleads.club/api/v1/crosswalk?q=MCC 5812` — or `?system=sic&code=1711`, or `?q=google category plumber`, or plain words (`?q=restaurants`). `states` (comma list) narrows the live count; empty means every live state. Over MCP: `explain_concept("MCC 5812")`.

The reply:
- `interpreted_as` — the system, the code and its label.
- `industries[]` — our industries it ties to, each marked `exact` (carries that code itself) or `related` (tied to it through the NAICS crosswalk), with its code in all four systems and its live `count`.
- `equivalents` — the matching codes in each system, with labels. Each says how it got there: via industry (a code one of our industries under your input carries) or via concordance (a code the public concordance ties to the same NAICS, which can reach past the trade — MCC 5812 reaches SIC 5461 Retail Bakeries this way). The ready `filters` carry the industry codes; concordance codes join only when no industry of ours carries a code in that system.
- `filters` — the exact filter for each system (`naics_6_digit`, `sic_4_digit`, `gmb_category`, `mcc`) and for our industry names. Hand one to the count, the cross-tab or the quote.
- `total` — the whole crosswalk neighborhood; `total_exact` — only the industries that carry the code itself.

## It widens, it does not stop

A code we do not carry directly widens: to its parent group (SIC 1712 → 171*), then to the industries the crosswalk ties it to. `widened` says which step it took. Only a code nothing relates to comes back empty, and then `note` names where to go. A SIC or NAICS prefix (`17`, `238`) is a whole group. In plain words (`interpret_list`, `/api/v1/lists/interpret`), "SIC 1711", "MCC 5812", "NAICS 238220" and "google category plumber" each become a filter, and an unknown code widens the same way and says so.

## Provenance

SIC↔NAICS is the Census concordance. MCC and Google category tie to NAICS through mappings we curate, because no public concordance exists for them, so every industry reports its mapping confidence (`clean` or an approximate tier) rather than claiming more than it knows. Records are classified from the filing at formation; a business not yet placed reads "Still classifying", and every pipeline run places more.

## Then size a territory

Classification and geography are the two ways a buyer builds a territory. Cross-tab them in one call (`group_by` on the count — see /counts.llms.txt): by metro, county, city, ZIP or neighborhood on one side, NAICS, SIC, Google category or MCC on the other.