# Støj

> Façade Lden (day-evening-night road noise) for one Danish address. Keyless. No signup.

The agent front door is the docs page. GET and POST /api/noise return the same JSON. Both are safe reads and share a per-IP quota (60/minute by default, HTTP 429 with Retry-After).

## When to use this

When to use this: call Støj when an agent needs façade road noise (vejstøj) for one Danish street address. That includes a støjkort-style Lden (day-evening-night) figure, official København façade values, or a labeled estimate outside Copenhagen. Do not use it for garden noise, indoor noise, rail or air noise, or a paid contour map. The first call is keyless GET or POST /api/noise. No signup.

Hvornår du skal bruge det: kald Støj, når en agent skal bruge vejstøj på facaden for én dansk adresse. Det dækker et støjkort-agtigt Lden-tal (dag-aften-nat), officielle Københavnske facadeværdier, eller et mærket estimat uden for København. Brug det ikke til haven, indendørs støj, jernbane eller fly, eller et betalt konturkort. Første kald er uden nøgle: GET eller POST /api/noise. Ingen tilmelding.

## Docs

- Docs: https://stoj.multihead.dev/docs
- OpenAPI: https://stoj.multihead.dev/openapi.yaml
- Skill: https://stoj.multihead.dev/SKILL.md
- This index: https://stoj.multihead.dev/llms.txt

## Call

GET (browsing agents):

```
curl -sS 'https://stoj.multihead.dev/api/noise?address=Smedev%C3%A6nget%202%2C%204100%20Ringsted'
```

POST (same JSON):

```
curl -sS -X POST https://stoj.multihead.dev/api/noise \
  -H 'content-type: application/json' \
  -d '{"address":"Smedevænget 2, 4100 Ringsted"}'
```

Branch on the HTTP code and the `status` field (`ok`, `estimated`, `outside_copenhagen`, `no_facade`, `unresolved`, `error`). A finished miss has no dB. Do not invent one.

Copenhagen: official façade, source label "Københavns Kommune, beregnet vejstøj 2022 (Nord2000)". Outside Copenhagen: labelled 007-traffic-diff estimate, `officialFacade` false. Modelled estimate, not an official noise map. Independent København sample, N=200: bias +1.3 dB, MAE 4.8 dB, 41.0% within ±3 dB. It reads low on loud façades (≥68 dB truth band: bias −2.6 dB, N=50). A point below 50 dB is low confidence: on the København hold-out that band covered 50% of truths (2 of 4), against a nominal 80%. That error was measured in København only, so outside København it is an untested extrapolation.

`POST /api/address-noise` needs header X-Api-Key. Keys are not self-serve. There is no paid signup. Use /api/noise for the first call.

`GET /api/health` is a reachability check, not the product answer.