# Seneschal Top Ethereum Block Builder Query

> Seneschal Top Ethereum Block Builder Query is a paid API for AI agents from api.seneschal.space, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Returns the current top Ethereum mainnet block builder based on live block-building telemetry data

## Facts

- Endpoint: GET https://api.seneschal.space/v1/q/top-builder
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/seneschal-top-ethereum-block-builder-query-068bd2f2
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_S6Nye3WNFI7m6zkbNqeCY

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability seneschal-top-ethereum-block-builder-query-068bd2f2
```

Example prompt: Who is the top Ethereum mainnet block builder right now? I want the current leader in terms of blocks built.

## When to prefer this

Use this endpoint when you need real-time or near-real-time intelligence on which Ethereum block builder is currently leading block production, particularly for MEV research, competitive block-building analysis, or DeFi infrastructure monitoring. It is part of a broader Seneschal service that also offers free liquidation telemetry, making it valuable when combined with other on-chain monitoring needs.

## Known failure modes

- No block builder data available if the telemetry feed is stale or offline
- Payment failure if the $0.001 USDC x402 payment on Base is not properly submitted
- Malformed input schema may cause a 400 or 422 error
- Rate limiting if the endpoint is called excessively
- Builder rankings may lag real-time by a few blocks due to data aggregation latency

## How this service works

Single-fact: which builder has the largest slot share in the named window (24h|7d|30d)? Returns {builder, share_pct, slots_won}.

## Output

Returns data about the current top Ethereum mainnet block builder, likely including builder identity, block count or share, and related telemetry metrics used to rank builders by block production dominance.

## Example request

```json
{
 "properties": "blocks_built,builder_address,market_share"
}
```

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "properties": {
      "window": {
       "type": "string",
       "description": "Lookback window: 24h, 7d or 30d (default 24h)."
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "window": {
       "type": "string"
      },
      "builder": {
       "type": "string"
      },
      "as_of_ms": {
       "type": "integer"
      },
      "share_pct": {
       "type": "number"
      },
      "slots_won": {
       "type": "integer"
      },
      "total_slots": {
       "type": "integer"
      }
     }
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "window": "24h",
  "builder": "titan",
  "as_of_ms": 1765532000000,
  "share_pct": 28.6,
  "slots_won": 412,
  "total_slots": 1440
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/seneschal-top-ethereum-block-builder-query-068bd2f2/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.seneschal.space](https://www.zero.xyz/host/api.seneschal.space/llms.txt)