mev-mcp

An MCP server for inspecting MEV-relevant activity on Polygon — pending mempool traffic, confirmed swap history, and gas pricing — exposed as tools an AI agent (or you, via Claude Desktop) can call directly.

This is a diagnostic and research tool, not a production MEV detector. It's built to be honest about what it sees and what it misses, rather than to look more capable than it is.

What it does

Polygon only. Arbitrum uses a centralized sequencer with no public mempool, so pending-transaction tools aren't meaningful there.

The honest part: mempool coverage is partial, and the tool tells you so

Swaps on a given pool can be routed through many different contracts — Uniswap's own SwapRouter, SwapRouter02, UniversalRouter, or any of a long list of aggregators (1inch, Odos, Paraswap, and others). check_pending_swaps_on_pool currently decodes:

• Direct calls to the pool contract
• SwapRouter / SwapRouter02 single-hop swaps (exactInputSingle, exactOutputSingle) and multi-hop swaps (exactInput, exactOutput, via packed-path decoding)
• UniversalRouter V3_SWAP_EXACT_IN / V3_SWAP_EXACT_OUT commands
• 1inch AggregationRouter v6 swaps

That's a meaningful slice of mempool traffic, but it is not exhaustive. In testing on a moderately active Polygon pool, well over half of confirmed swap volume routed through contracts outside this list — other aggregators, smart-contract wallets, and routing contracts we haven't decoded yet.

Rather than let that show up as a silent count: 0 — indistinguishable from "this pool is just quiet" — check_pending_swaps_on_pool runs a quick confirmed-swap check over a comparable window and returns a coverage_estimate field alongside the raw count:

{
  "count": 0,
  "routes": { "router_swap": 0, "universal_router_swap": 0, "aggregator_1inch": 0, "direct_pool_call": 0 },
  "confirmed_check": { "swap_count": 4, "by_to_address": { "...": 1 } },
  "coverage_estimate": "low — confirmed swaps exist on this pool but none were caught pending; likely routed through unrecognized contracts"
}

Possible coverage_estimate values:

• no_recent_activity — no confirmed swaps in the last N blocks (~M min); this pool appears genuinely inactive — confirmed window large enough (≥300 blocks) to trust a zero result
• inconclusive — … window too short to draw conclusions — confirmed window smaller than the minimum reliable threshold
• low — confirmed swaps exist on this pool but none were caught pending; likely routed through unrecognized contracts — pool is active but none of the pending transactions matched a known router
• low / medium / high (ratio R: N pending caught vs M confirmed) — at least some pending matches found; ratio against confirmed volume gives a coverage signal
• unknown — confirmed check failed: ExceptionType: message — the self-check itself threw an exception; raw count still stands
• unknown — confirmed check returned error: … — RPC or other error from the confirmed check endpoint

If you need a quick, reliable read on whether a pool is active at all — independent of mempool coverage — use check_confirmed_swaps_on_pool directly. It reads finalized blocks, so it has no router-coverage blind spot, only the same long-tail-of-aggregators caveat in its by_to_address breakdown (you'll see contract addresses it doesn't attempt to label).

Requirements

• Python 3.10+
• An RPC provider for Polygon with mempool (eth_subscribe) support — most free-tier providers (including Alchemy's free tier) support this for newPendingTransactions
• For check_confirmed_swaps_on_pool: an eth_getLogs-capable endpoint. Free-tier plans often cap the block range per call (Alchemy's free tier: 10 blocks); the tool chunks requests automatically, configurable via MEV_MCP_LOGS_CHUNK_SIZE (default 10). On a paid plan, raising this (e.g. to 500) significantly speeds up confirmed-swap lookups.

Setup

git clone https://github.com/matiosera3-ops/mev-mcp
cd mev-mcp
pip install -e .

Add to your Claude Desktop config (claude_desktop_config.json):

{
  "mcpServers": {
    "mev-mcp": {
      "command": "python",
      "args": ["-m", "mev_mcp.server"],
      "env": {
        "POLYGON_RPC_URL": "https://your-polygon-rpc-url",
        "MEV_MCP_LOGS_CHUNK_SIZE": "10"
      }
    }
  }
}

Not yet published to PyPI — install from source for now.

Known limitations

• Router coverage is partial. See above. Contributions adding decoders for additional aggregators (Odos, Paraswap, 0x) are welcome — the existing SwapRouter/UniversalRouter/1inch decoders in pending_swaps.py are a template for the calldata-matching pattern used.
• Mempool visibility depends on your RPC provider. Different providers see different shares of the public mempool. hashes_seen / hashes_resolved in the raw tool output give you a sense of how much traffic your provider surfaces.
• Free-tier `eth_getLogs` limits make `check_confirmed_swaps_on_pool` slow on a free Alchemy plan (chunking in 10-block calls). Fine for occasional diagnostic use; not built for high-frequency polling.
• No Arbitrum mempool support, structurally — there isn't a public one to watch.

License

MIT