# MEV-Boost Builder Market Share

> MEV-Boost Builder Market Share is a paid API for AI agents from agent402.tools, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-14).

Aggregates block-builder market share statistics over a recent window of MEV-Boost blocks via the Flashbots relay, returning per-builder block counts, share percentages, and ETH paid to proposers.

## Facts

- Endpoint: POST https://agent402.tools/api/mev-builder-share
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/mev-boost-builder-market-share-5eb7aa32
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_wtI2dGU9QjxOeUKlujRbl

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 mev-boost-builder-market-share-5eb7aa32 -d '<json body>'
```

Example prompt: Show me the block-builder market share and ETH paid to proposers aggregated over the last 50 MEV-Boost blocks via the Flashbots relay, so I can see if any builder is dominating or a new one is gaining ground.

## When to prefer this

Use this endpoint when you need a quick, aggregated snapshot of Ethereum block-builder concentration from the Flashbots relay without having to query raw relay data yourself. Ideal for monitoring builder centralization trends, detecting new entrants, or computing proposer revenue statistics over a sliding window of recent blocks.

## Known failure modes

- window parameter out of range (must be 10-200) returns a validation error
- Flashbots relay data temporarily unavailable causes a service error
- payment failure or insufficient USDC balance prevents the call from completing
- malformed request body returns a 400 bad request
- window set too small may return noisy or unrepresentative share data

## How this service works

Builder market share aggregated over the last N MEV-Boost blocks via the Flashbots relay. Returns per-builder block count, share percent, total ETH paid to proposers, and average per block. Use to track block-builder concentration or detect a new builder gaining share.

## Output

A list of block builders with their individual block counts, market share percentage, total ETH paid to proposers, and average ETH paid per block — computed over the requested window of recent MEV-Boost blocks from the Flashbots relay.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "window": {
   "type": "number",
   "description": "Recent blocks to aggregate (10-200, default 100)."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "relay": "flashbots",
  "builders": [
   {
    "blocks": 42,
    "sharePct": 42,
    "builderShort": "0x90000000…abcdef",
    "builderPubkey": "0x9000...",
    "avgEthPerBlock": 0.082305,
    "totalEthToProposers": 3.456789
   }
  ],
  "windowBlocks": 100,
  "uniqueBuilders": 5
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/mev-boost-builder-market-share-5eb7aa32/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent402.tools](https://www.zero.xyz/host/agent402.tools/llms.txt)