> ## Documentation Index
> Fetch the complete documentation index at: https://kremis.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# POST /certify

> Execute a query and return a Verifiable Query Certificate.

<ParamField path="method" type="POST">
  `/certify`
</ParamField>

**Authentication:** Required (if enabled)

Executes the same query as [`POST /query`](/api/query-lookup), then returns a
Verifiable Query Certificate (VQC): a deterministic, base64-encoded object a
third party re-derives offline to re-verify the result. See
[Proof-Carrying Knowledge](/concepts/proof-carrying-knowledge) and the
[Certificate Specification](/concepts/certificate-spec).

## Request Body

Identical to `/query` — the tagged `QueryRequest`.

```json theme={null}
{ "type": "lookup", "entity_id": 12345678901234567 }
```

| Field            | Type   | Required | Description                                                                                         |
| ---------------- | ------ | -------- | --------------------------------------------------------------------------------------------------- |
| `type`           | string | Yes      | Query variant (`lookup`, `traverse`, `traverse_filtered`, `strongest_path`, `intersect`, `related`) |
| *variant fields* | —      | Yes      | Same fields as the matching `/query` variant                                                        |

<Note>
  The `properties` variant is **not** certifiable: the certificate format
  carries only canonical node/edge evidence, with no field for property values,
  so it returns `400 Bad Request`.
</Note>

## Response

| Field              | Type           | Description                                                                        |
| ------------------ | -------------- | ---------------------------------------------------------------------------------- |
| `success`          | boolean        | Whether the certificate was produced                                               |
| `found`            | boolean        | Whether the query found supporting data                                            |
| `grounding`        | string         | `fact`, `inference`, or `unknown`                                                  |
| `proof_of_absence` | boolean        | True when a certified `unknown` with empty evidence proves absence at `state_hash` |
| `state_hash`       | string \| null | BLAKE3 hex digest of the canonical (`KREX`) state                                  |
| `certificate`      | string \| null | Base64 canonical bytes — magic `KVQC`, version 1                                   |
| `error`            | string \| null | Present only when `success` is `false`                                             |

<CodeGroup>
  ```json Certified fact theme={null}
  {
    "success": true,
    "found": true,
    "grounding": "fact",
    "proof_of_absence": false,
    "state_hash": "a3b4c5d6e7f8a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a1b2c3d4e5f6a7b8",
    "certificate": "S1ZRQw...",
    "error": null
  }
  ```

  ```json Proof of absence theme={null}
  {
    "success": true,
    "found": false,
    "grounding": "unknown",
    "proof_of_absence": true,
    "state_hash": "a3b4c5d6e7f8a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a1b2c3d4e5f6a7b8",
    "certificate": "S1ZRQw...",
    "error": null
  }
  ```

  ```json 400 (properties) theme={null}
  {
    "success": false,
    "found": false,
    "grounding": "unknown",
    "proof_of_absence": false,
    "state_hash": null,
    "certificate": null,
    "error": "Properties queries are not certifiable: the certificate format carries no property evidence"
  }
  ```
</CodeGroup>

## Example

```bash theme={null}
curl -X POST http://localhost:8080/certify \
  -H "Content-Type: application/json" \
  -d '{"type":"lookup","entity_id":12345678901234567}'
# response: { "success": true, "found": true, "grounding": "fact", ... }
```

A verifier decodes `certificate`, re-runs it against a graph whose canonical
export hashes to `state_hash`, and compares bytes. Equality re-verifies the
result without trusting this server.