# 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`.

  - `error: { code, message, details}`

    Error payload

    - `code: String`

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

    - `message: String`

      Human-readable explanation of what went wrong

    - `details: Hash[Symbol, untyped]`

      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`.

  - `features: Array[GeoJsonFeature]`

    Array of GeoJSON Feature objects

    - `geometry: GeoJsonGeometry`

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

      - `coordinates: Array[Float] | Array[Array[Float]] | Array[Array[Array[Float]]] | Array[Array[Array[Array[Float]]]]`

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

        - `Array[Float]`

          [longitude, latitude] or [longitude, latitude, elevation]

        - `Array[Array[Float]]`

          Array of [lng, lat] positions

        - `Array[Array[Array[Float]]]`

          Array of linear rings / line strings

        - `Array[Array[Array[Array[Float]]]]`

          Array of polygons

      - `type: :Point | :LineString | :Polygon | 3 more`

        Geometry type

        - `:Point`

        - `:LineString`

        - `:Polygon`

        - `:MultiPoint`

        - `:MultiLineString`

        - `:MultiPolygon`

    - `properties: Hash[Symbol, untyped]`

      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.

    - `type: :Feature`

      Always `Feature`

      - `:Feature`

    - `id: String`

      Compound identifier in `type/osm_id` format

  - `type: :FeatureCollection`

    Always `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.

  - `geometry: GeoJsonGeometry`

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

    - `coordinates: Array[Float] | Array[Array[Float]] | Array[Array[Array[Float]]] | Array[Array[Array[Array[Float]]]]`

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

      - `Array[Float]`

        [longitude, latitude] or [longitude, latitude, elevation]

      - `Array[Array[Float]]`

        Array of [lng, lat] positions

      - `Array[Array[Array[Float]]]`

        Array of linear rings / line strings

      - `Array[Array[Array[Array[Float]]]]`

        Array of polygons

    - `type: :Point | :LineString | :Polygon | 3 more`

      Geometry type

      - `:Point`

      - `:LineString`

      - `:Polygon`

      - `:MultiPoint`

      - `:MultiLineString`

      - `:MultiPolygon`

  - `properties: Hash[Symbol, untyped]`

    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.

  - `type: :Feature`

    Always `Feature`

    - `:Feature`

  - `id: String`

    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.

  - `coordinates: Array[Float] | Array[Array[Float]] | Array[Array[Array[Float]]] | Array[Array[Array[Array[Float]]]]`

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

    - `Array[Float]`

      [longitude, latitude] or [longitude, latitude, elevation]

    - `Array[Array[Float]]`

      Array of [lng, lat] positions

    - `Array[Array[Array[Float]]]`

      Array of linear rings / line strings

    - `Array[Array[Array[Array[Float]]]]`

      Array of polygons

  - `type: :Point | :LineString | :Polygon | 3 more`

    Geometry type

    - `:Point`

    - `:LineString`

    - `:Polygon`

    - `:MultiPoint`

    - `:MultiLineString`

    - `:MultiPolygon`