# Builder | API reference | Femtos

> One builder code: totals and rank, day by day, per market, order outcomes and fee rates. GET /v1/hypercore/builders/{builder} on HyperCore: parameters, response fields and a live call per layer.

- Base URL: `https://api.femtos.xyz/v1` (REST) · `wss://api.femtos.xyz/v1/ws` (WebSocket) · MCP: `https://api.femtos.xyz/mcp`
- Auth: `Authorization: Bearer $FEMTOS_KEY`. Free key: https://dashboard.femtos.xyz/signup (browser), or with
  no browser: `GET https://femtos.xyz/accounts/agent/challenge`, solve its proof of work, then `POST https://femtos.xyz/accounts/agent/signup`
  (https://femtos.xyz/agents.md#agent-onboarding)
- Decimals are exact strings, times Unix milliseconds, addresses lowercase `0x`
- Whole API in one file: https://femtos.xyz/agents.md · OpenAPI: https://api.femtos.xyz/v1/openapi.json · Index: https://femtos.xyz/llms.txt
- Page with live calls: https://femtos.xyz/reference/builder

## Builder — GET `/v1/hypercore/builders/{builder}`

One builder code: totals and rank, day by day, per market, order outcomes and fee rates.

Layers: HyperCore. Not on Elysium or HyperEVM: served on HyperCore only.
Page with live calls: https://femtos.xyz/reference/builder?layer=hypercore

| Param | In | Example or values | Meaning |
|---|---|---|---|
| `builder` | path | `0xb84168cf3be63c6b8dad05ff5d755e97432ff80b` | Builder address (0x), as orders name it in `builder.b` |
| `window` | query | `(empty)`, `24h`, `7d`, `30d`, `90d`, `all` | Window, whole hours ending with the current one: 24h, 7d, 30d, 90d, or all (since 2025-07-19) |

```bash
curl -H "Authorization: Bearer $FEMTOS_KEY" "https://api.femtos.xyz/v1/hypercore/builders/0xb84168cf3be63c6b8dad05ff5d755e97432ff80b?window=30d"
```

| Field | Type | Meaning |
|---|---|---|
| `total` | object | Over the window: {fees, feesByToken, volume, fills, takerFills, users, feeRate, feeShare, orders} |
| `rank` | int \| null | Rank by fees among every builder in the window; null with no fill in it |
| `daily[]` | object | UTC days of the window with a fill, oldest first: {day, fees, volume, fills, users} |
| `markets[]` | object | Its markets, most fees first (100 at most): {coin, quote, fees, volume, feeRate, fills, users} |
| `orders` | object \| null | Its order statuses in the window; null for a window ending before order coverage: {orders, byStatus, feeRates} |
| `orders.byStatus[]` | object | Most first: {status, events, orders} |
| `orders.feeRates[]` | object | Most orders first: {feeTenthsBp, orders} |

## Related (Builder codes)

- [Builder leaderboard](https://femtos.xyz/reference/builders.md) `GET /v1/hypercore/builders`: Every builder code ranked by fees, volume, users or orders, over 24 h to all time. (HyperCore)
- [Builder orders](https://femtos.xyz/reference/builder-orders.md) `GET /v1/hypercore/builders/{builder}/orders`: Every status of the orders sent with one builder code, rejections and their reasons included. (HyperCore)
- [Builder orders stream](https://femtos.xyz/reference/ws/builder-orders.md) `WS hc.builder.orders`: Every status of the orders sent with one builder code as it happens, rejections and their reasons included. One frame per block with all its matching events. (HyperCore)
- [Builder fills](https://femtos.xyz/reference/builder-fills.md) `GET /v1/hypercore/builders/{builder}/fills`: Every fill of one builder code, with its builder fee, oid, tid and hash. (HyperCore)
- [Builder fills stream](https://femtos.xyz/reference/ws/builder-fills.md) `WS hc.builder.fills`: Every fill of one builder code as it happens, with its builder fee: the rows of the builder fills route, pushed per block. One frame per block with all its matching events. (HyperCore)

Every page: https://femtos.xyz/reference.md