# Oracle On-Chain — Free Sample

**Cost:** free evaluation · **Settle canary:** $0.01 · **Challenge stake:** $0.01

## Free evaluation

```http
GET https://lvlltd.com/api/sco?op=eval&oracle=oracle-on-chain
```

Returns outline, free sample fields (`block_number`, `network`, `observed_at`), recent sealed packs, and **ledger-only** reputation (null until packs exist).

## Multi-source canary

```http
POST https://lvlltd.com/api/sco
Content-Type: application/json

{
  "op": "canary",
  "oracle_id": "oracle-on-chain",
  "providers": ["lvl-foundation-a", "lvl-foundation-b"]
}
```

Each provider returns a sealed, content-addressed pack with `challengeable: true`.

## Consensus

```http
POST https://lvlltd.com/api/sco
{"op":"consensus","input_cids":["sco_…","sco_…"]}
```

## Challenge

```http
POST https://lvlltd.com/api/sco
{
  "op": "challenge",
  "target_cid": "sco_…",
  "counter_proof": {"type":"counter_observation","claim":"block too high","payload":{}},
  "stake_usd": 0.01
}
```

Honesty: no claim is trusted without a public sealed proof that is challengeable.