# Client

## Domain Types

### Error

- `class Error:`

  Standard API error envelope. Every error response wraps a single `error` object with a machine-readable `code`, a human-readable `message`, and optional structured `details`.

  - `required Error Error`

    Error payload

    - `required string Code`

      Machine-readable error code (e.g. `invalid_request`, `not_found`, `rate_limited`, `query_error`, `daily_limit_exceeded`)

    - `required string Message`

      Human-readable explanation of what went wrong

    - `IReadOnlyDictionary<string, JsonElement>? Details`

      Structured details when available (e.g. field-level validation errors, rate limit metadata, billing info)

### Feature Collection

- `class FeatureCollection:`

  GeoJSON FeatureCollection (RFC 7946). For paginated endpoints, metadata is returned in HTTP response headers rather than the body:

| Header          | Description                                      |
| --------------- | ------------------------------------------------ |
| `X-Limit`       | Requested result limit                           |
| `X-Has-More`    | `true` if more results exist                     |
| `X-Next-Cursor` | Opaque cursor for next page (cursor pagination)  |
| `X-Next-Offset` | Numeric offset for next page (offset pagination) |
| `Link`          | RFC 8288 `rel="next"` link to the next page      |

  Content-Type is `application/geo+json`.

  - `required IReadOnlyList<GeoJsonFeature> Features`

    Array of GeoJSON Feature objects

    - `required GeoJsonGeometry Geometry`

      GeoJSON Geometry object per RFC 7946. Coordinates use [longitude, latitude] order. 3D coordinates [lng, lat, elevation] are used for elevation endpoints.

      - `required Coordinates Coordinates`

        Coordinates array. Nesting depth varies by geometry type: Point = [lng, lat], LineString = [[lng, lat], ...], Polygon = [[[lng, lat], ...], ...], etc.

        - `IReadOnlyList<Double>`

        - `IReadOnlyList<IReadOnlyList<Double>>`

        - `IReadOnlyList<IReadOnlyList<IReadOnlyList<Double>>>`

        - `IReadOnlyList<IReadOnlyList<IReadOnlyList<IReadOnlyList<Double>>>>`

      - `required Type Type`

        Geometry type

        - `"Point"Point`

        - `"LineString"LineString`

        - `"Polygon"Polygon`

        - `"MultiPoint"MultiPoint`

        - `"MultiLineString"MultiLineString`

        - `"MultiPolygon"MultiPolygon`

    - `required IReadOnlyDictionary<string, JsonElement> Properties`

      OSM tags flattened as key-value pairs, plus `@type` (node/way/relation) and `@id` (OSM ID) metadata fields. May include `distance_m` for proximity queries.

    - `required Type Type`

      Always `Feature`

      - `"Feature"Feature`

    - `string ID`

      Compound identifier in `type/osm_id` format

  - `required Type Type`

    Always `FeatureCollection`

    - `"FeatureCollection"FeatureCollection`

### Geo Json Feature

- `class GeoJsonFeature:`

  GeoJSON Feature representing an OSM element. Tags from the original OSM element are flattened directly into `properties` (not nested under a `tags` key). Metadata fields `@type` and `@id` identify the OSM element type and ID within properties.

  - `required GeoJsonGeometry Geometry`

    GeoJSON Geometry object per RFC 7946. Coordinates use [longitude, latitude] order. 3D coordinates [lng, lat, elevation] are used for elevation endpoints.

    - `required Coordinates Coordinates`

      Coordinates array. Nesting depth varies by geometry type: Point = [lng, lat], LineString = [[lng, lat], ...], Polygon = [[[lng, lat], ...], ...], etc.

      - `IReadOnlyList<Double>`

      - `IReadOnlyList<IReadOnlyList<Double>>`

      - `IReadOnlyList<IReadOnlyList<IReadOnlyList<Double>>>`

      - `IReadOnlyList<IReadOnlyList<IReadOnlyList<IReadOnlyList<Double>>>>`

    - `required Type Type`

      Geometry type

      - `"Point"Point`

      - `"LineString"LineString`

      - `"Polygon"Polygon`

      - `"MultiPoint"MultiPoint`

      - `"MultiLineString"MultiLineString`

      - `"MultiPolygon"MultiPolygon`

  - `required IReadOnlyDictionary<string, JsonElement> Properties`

    OSM tags flattened as key-value pairs, plus `@type` (node/way/relation) and `@id` (OSM ID) metadata fields. May include `distance_m` for proximity queries.

  - `required Type Type`

    Always `Feature`

    - `"Feature"Feature`

  - `string ID`

    Compound identifier in `type/osm_id` format

### Geo Json Geometry

- `class GeoJsonGeometry:`

  GeoJSON Geometry object per RFC 7946. Coordinates use [longitude, latitude] order. 3D coordinates [lng, lat, elevation] are used for elevation endpoints.

  - `required Coordinates Coordinates`

    Coordinates array. Nesting depth varies by geometry type: Point = [lng, lat], LineString = [[lng, lat], ...], Polygon = [[[lng, lat], ...], ...], etc.

    - `IReadOnlyList<Double>`

    - `IReadOnlyList<IReadOnlyList<Double>>`

    - `IReadOnlyList<IReadOnlyList<IReadOnlyList<Double>>>`

    - `IReadOnlyList<IReadOnlyList<IReadOnlyList<IReadOnlyList<Double>>>>`

  - `required Type Type`

    Geometry type

    - `"Point"Point`

    - `"LineString"LineString`

    - `"Polygon"Polygon`

    - `"MultiPoint"MultiPoint`

    - `"MultiLineString"MultiLineString`

    - `"MultiPolygon"MultiPolygon`