# Compute facets for a result set

`GET /discovery/v1/facets`

Compute facets for a previously executed search or listing.

Rate limited: a ``429`` carries ``Retry-After``.

Facets are computed over the result set identified by ``guid``: per-field
values for a keyword field, min/max bounds for a numeric one.

## Request example

```bash
curl --request GET \
  --url 'https://api.eu1.luigisbox.ai/discovery/v1/facets?channel_id=<channel_id>&guid=<guid>&facet_fields=<facet_fields>&debug=false' \
  --header 'Authorization: Bearer <access_token>'
```

## Query Parameters

| Name | Type | Required | Description | Constraints |
|---|---|---|---|---|
| `channel_id` | `string` | Yes | Channel identifier (serving destination). | >= 1 characters |
| `guid` | `string` | Yes | GUID from a prior /search or /listing response to facet on. | >= 1 characters |
| `facet_fields` | `string` | Yes | Comma-separated facet fields. Each entry is a plain field name or 'name^count' where count limits the number of returned keyword facet values (positive integer). Use '^' for namespaced fields, e.g. 'lbx:price^30'. The 'name:count' form is also accepted. | — |
| `hierarchy_anchor` | `Array<string>` | No | Open branches to expand in hierarchical facets. Each value is '<field>:<node_path>' where node_path is the fully expanded, ' > '-joined node path (e.g. 'lbx:category_hierarchy:category/jewelry > category/rings'). Repeatable across fields and open branches; omitted expands roots only. | — |
| `hierarchy_depth` | `Array<string>` | No | Requested child-level expansion for hierarchical facets. Each value is '<field>:<depth>' where depth is the number of child levels to expand from the roots and must be between 1 and 5 (e.g. 'lbx:category_hierarchy:5'). A field may appear at most once. Values outside the range, non-integers, and repeated fields are rejected with 422. | — |
| `debug` | `boolean` | No | Request ranking diagnostics. Honoured only on the first page for callers holding ``discovery:debug``; silently ignored otherwise. | — |

## Responses

| Status | Description | Content |
|---|---|---|
| `200` | Successful Response | application/json: object |
| `400` | Malformed request | application/json: object |
| `401` | Missing or invalid credentials | application/json: object |
| `403` | Authenticated but not permitted | application/json: object |
| `404` | Resource not found | application/json: object |
| `422` | Request validation failed | application/json: object |
| `429` | Rate limit exceeded | application/json: object |
| `502` | Upstream service failed | application/json: object |

### 200

Successful Response

#### application/json

Schema: `object`

##### Attributes

| Attribute | Type | Required | Description | Constraints |
|---|---|---|---|---|
| `debug` | `anyOf(object, null)` | No | Ranking diagnostics — an open object whose contents carry no compatibility guarantee. Populated only when the caller passed ``debug=true`` AND holds the ``discovery:debug`` permission. Omitted from the response otherwise. | — |
| `debug.*` | `any` | No | Additional property. | — |
| `facets` | `object` | Yes | Per-field facet aggregation results. Values, bounds and counts cover only the objects this channel can serve. | — |
| `facets.*` | `anyOf(object, object, object)` | No | Additional property. | — |
| `facets.*.field` | `string` | Yes | The faceted field name. | — |
| `facets.*.type` | `string` | No | Type | allowed value: terms |
| `facets.*.values` | `Array<string>` | No | Values | — |
| `facets.*.max` | `number` | Yes | Maximum value in the result set. | — |
| `facets.*.min` | `number` | Yes | Minimum value in the result set. | — |
| `facets.*.values[].children` | `Array<object>` | No | Child nodes populated along an open branch. | — |
| `facets.*.values[].has_children` | `boolean` | Yes | Whether the node has expandable descendants. | — |
| `facets.*.values[].title` | `string` | Yes | Display title of the node's own identity. | — |
| `facets.*.values[].value` | `string` | Yes | Fully expanded node path (segments joined by ' > '). | — |
| `guid` | `string` | Yes | GUID identifying this result set. | — |

##### Response example

```json
{
  "debug": {},
  "facets": {
    "additionalProperty": {
      "field": "example",
      "type": "terms",
      "values": [
        "example"
      ]
    }
  },
  "guid": "example"
}
```

### 400

Malformed request

#### application/json

Schema: `object`

##### Attributes

| Attribute | Type | Required | Description | Constraints |
|---|---|---|---|---|
| `exception_details` | `object` | No | Machine-readable error context; empty object when there is nothing to add. | — |
| `exception_details.validation_errors` | `anyOf(Array<object>, null)` | No | Every field-level problem found in the request, when validation is what failed. Absent when the rejection is not about a specific value. | — |
| `exception_details.validation_errors[].loc` | `Array<anyOf(string, integer)>` | Yes | Path to the offending value from the request root, e.g. `["body", "filters", 0, "operator"]`. | — |
| `exception_details.validation_errors[].msg` | `string` | Yes | What is wrong with the value at `loc`. | — |
| `exception_details.validation_errors[].type` | `string` | Yes | Stable machine code for the problem, e.g. `missing` or `string_too_short`. | — |
| `exception_details.*` | `any` | No | Additional property. | — |
| `reason` | `string` | Yes | Human-readable, actionable error message. | — |
| `request_id` | `anyOf(string, null)` | No | Request correlation ID (matches the X-Request-Id response header). | — |

##### Response example

```json
{
  "exception_details": {
    "validation_errors": [
      {
        "loc": [
          "example"
        ],
        "msg": "example",
        "type": "example"
      }
    ]
  },
  "reason": "example",
  "request_id": "example"
}
```

### 401

Missing or invalid credentials

#### application/json

Schema: `object`

##### Attributes

| Attribute | Type | Required | Description | Constraints |
|---|---|---|---|---|
| `exception_details` | `object` | No | Machine-readable error context; empty object when there is nothing to add. | — |
| `exception_details.validation_errors` | `anyOf(Array<object>, null)` | No | Every field-level problem found in the request, when validation is what failed. Absent when the rejection is not about a specific value. | — |
| `exception_details.validation_errors[].loc` | `Array<anyOf(string, integer)>` | Yes | Path to the offending value from the request root, e.g. `["body", "filters", 0, "operator"]`. | — |
| `exception_details.validation_errors[].msg` | `string` | Yes | What is wrong with the value at `loc`. | — |
| `exception_details.validation_errors[].type` | `string` | Yes | Stable machine code for the problem, e.g. `missing` or `string_too_short`. | — |
| `exception_details.*` | `any` | No | Additional property. | — |
| `reason` | `string` | Yes | Human-readable, actionable error message. | — |
| `request_id` | `anyOf(string, null)` | No | Request correlation ID (matches the X-Request-Id response header). | — |

##### Response example

```json
{
  "exception_details": {
    "validation_errors": [
      {
        "loc": [
          "example"
        ],
        "msg": "example",
        "type": "example"
      }
    ]
  },
  "reason": "example",
  "request_id": "example"
}
```

### 403

Authenticated but not permitted

#### application/json

Schema: `object`

##### Attributes

| Attribute | Type | Required | Description | Constraints |
|---|---|---|---|---|
| `exception_details` | `object` | No | Machine-readable error context; empty object when there is nothing to add. | — |
| `exception_details.validation_errors` | `anyOf(Array<object>, null)` | No | Every field-level problem found in the request, when validation is what failed. Absent when the rejection is not about a specific value. | — |
| `exception_details.validation_errors[].loc` | `Array<anyOf(string, integer)>` | Yes | Path to the offending value from the request root, e.g. `["body", "filters", 0, "operator"]`. | — |
| `exception_details.validation_errors[].msg` | `string` | Yes | What is wrong with the value at `loc`. | — |
| `exception_details.validation_errors[].type` | `string` | Yes | Stable machine code for the problem, e.g. `missing` or `string_too_short`. | — |
| `exception_details.*` | `any` | No | Additional property. | — |
| `reason` | `string` | Yes | Human-readable, actionable error message. | — |
| `request_id` | `anyOf(string, null)` | No | Request correlation ID (matches the X-Request-Id response header). | — |

##### Response example

```json
{
  "exception_details": {
    "validation_errors": [
      {
        "loc": [
          "example"
        ],
        "msg": "example",
        "type": "example"
      }
    ]
  },
  "reason": "example",
  "request_id": "example"
}
```

### 404

Resource not found

#### application/json

Schema: `object`

##### Attributes

| Attribute | Type | Required | Description | Constraints |
|---|---|---|---|---|
| `exception_details` | `object` | No | Machine-readable error context; empty object when there is nothing to add. | — |
| `exception_details.validation_errors` | `anyOf(Array<object>, null)` | No | Every field-level problem found in the request, when validation is what failed. Absent when the rejection is not about a specific value. | — |
| `exception_details.validation_errors[].loc` | `Array<anyOf(string, integer)>` | Yes | Path to the offending value from the request root, e.g. `["body", "filters", 0, "operator"]`. | — |
| `exception_details.validation_errors[].msg` | `string` | Yes | What is wrong with the value at `loc`. | — |
| `exception_details.validation_errors[].type` | `string` | Yes | Stable machine code for the problem, e.g. `missing` or `string_too_short`. | — |
| `exception_details.*` | `any` | No | Additional property. | — |
| `reason` | `string` | Yes | Human-readable, actionable error message. | — |
| `request_id` | `anyOf(string, null)` | No | Request correlation ID (matches the X-Request-Id response header). | — |

##### Response example

```json
{
  "exception_details": {
    "validation_errors": [
      {
        "loc": [
          "example"
        ],
        "msg": "example",
        "type": "example"
      }
    ]
  },
  "reason": "example",
  "request_id": "example"
}
```

### 422

Request validation failed

#### application/json

Schema: `object`

##### Attributes

| Attribute | Type | Required | Description | Constraints |
|---|---|---|---|---|
| `exception_details` | `object` | No | Machine-readable error context; empty object when there is nothing to add. | — |
| `exception_details.validation_errors` | `anyOf(Array<object>, null)` | No | Every field-level problem found in the request, when validation is what failed. Absent when the rejection is not about a specific value. | — |
| `exception_details.validation_errors[].loc` | `Array<anyOf(string, integer)>` | Yes | Path to the offending value from the request root, e.g. `["body", "filters", 0, "operator"]`. | — |
| `exception_details.validation_errors[].msg` | `string` | Yes | What is wrong with the value at `loc`. | — |
| `exception_details.validation_errors[].type` | `string` | Yes | Stable machine code for the problem, e.g. `missing` or `string_too_short`. | — |
| `exception_details.*` | `any` | No | Additional property. | — |
| `reason` | `string` | Yes | Human-readable, actionable error message. | — |
| `request_id` | `anyOf(string, null)` | No | Request correlation ID (matches the X-Request-Id response header). | — |

##### Response example

```json
{
  "exception_details": {
    "validation_errors": [
      {
        "loc": [
          "example"
        ],
        "msg": "example",
        "type": "example"
      }
    ]
  },
  "reason": "example",
  "request_id": "example"
}
```

### 429

Rate limit exceeded

#### application/json

Schema: `object`

##### Attributes

| Attribute | Type | Required | Description | Constraints |
|---|---|---|---|---|
| `exception_details` | `object` | No | Machine-readable error context; empty object when there is nothing to add. | — |
| `exception_details.validation_errors` | `anyOf(Array<object>, null)` | No | Every field-level problem found in the request, when validation is what failed. Absent when the rejection is not about a specific value. | — |
| `exception_details.validation_errors[].loc` | `Array<anyOf(string, integer)>` | Yes | Path to the offending value from the request root, e.g. `["body", "filters", 0, "operator"]`. | — |
| `exception_details.validation_errors[].msg` | `string` | Yes | What is wrong with the value at `loc`. | — |
| `exception_details.validation_errors[].type` | `string` | Yes | Stable machine code for the problem, e.g. `missing` or `string_too_short`. | — |
| `exception_details.*` | `any` | No | Additional property. | — |
| `reason` | `string` | Yes | Human-readable, actionable error message. | — |
| `request_id` | `anyOf(string, null)` | No | Request correlation ID (matches the X-Request-Id response header). | — |

##### Response example

```json
{
  "exception_details": {
    "validation_errors": [
      {
        "loc": [
          "example"
        ],
        "msg": "example",
        "type": "example"
      }
    ]
  },
  "reason": "example",
  "request_id": "example"
}
```

### 502

Upstream service failed

#### application/json

Schema: `object`

##### Attributes

| Attribute | Type | Required | Description | Constraints |
|---|---|---|---|---|
| `exception_details` | `object` | No | Machine-readable error context; empty object when there is nothing to add. | — |
| `exception_details.validation_errors` | `anyOf(Array<object>, null)` | No | Every field-level problem found in the request, when validation is what failed. Absent when the rejection is not about a specific value. | — |
| `exception_details.validation_errors[].loc` | `Array<anyOf(string, integer)>` | Yes | Path to the offending value from the request root, e.g. `["body", "filters", 0, "operator"]`. | — |
| `exception_details.validation_errors[].msg` | `string` | Yes | What is wrong with the value at `loc`. | — |
| `exception_details.validation_errors[].type` | `string` | Yes | Stable machine code for the problem, e.g. `missing` or `string_too_short`. | — |
| `exception_details.*` | `any` | No | Additional property. | — |
| `reason` | `string` | Yes | Human-readable, actionable error message. | — |
| `request_id` | `anyOf(string, null)` | No | Request correlation ID (matches the X-Request-Id response header). | — |

##### Response example

```json
{
  "exception_details": {
    "validation_errors": [
      {
        "loc": [
          "example"
        ],
        "msg": "example",
        "type": "example"
      }
    ]
  },
  "reason": "example",
  "request_id": "example"
}
```