Best Blockchain MCP Servers for AI agents.

Blockchain servers here fall into three working groups. Developer tooling: Ethereum Transaction Builder constructs and signs EIP-1559 transactions with gas estimation and ERC-20 transfers; its sibling servers handle address validation and EIP-712 message signing; iz-tolk-mcp compiles Tolk contracts for TON. These turn an AI assistant into a competent chain developer's pair.

Then there are generators and aggregators — UCAI converts any smart contract ABI into a ready-made MCP server, which is a meta-tool: one command and an arbitrary deployed contract becomes agent-callable. And finally live data feeds: Gas Oracle API serves real-time gas prices for Base and Ethereum, DEX Swap Quotes API compares quotes across Uniswap, SushiSwap, and Aerodrome, and the Solana Priority Fee Estimator reads congestion in real time.

Any agent that transacts — including one paying for its own MCP calls in USDC on Base — eventually needs to reason about the chain it transacts on. Before submitting a transaction it should know current gas conditions; before executing a swap it should compare venues; before trusting an address it should validate the checksum. The data servers in this list answer exactly those pre-flight questions.

The developer-tooling servers serve a different agent: the coding assistant working on contracts, where compile-check-deploy loops and typed-data signing are the daily grind.

Key handling first. Servers that sign transactions or messages touch private keys — understand whether keys stay local, and never hand a hot key with real funds to an experimental setup. Second, freshness guarantees: gas prices and swap quotes decay in seconds, so a data server's value is its latency, which is worth testing before an agent depends on it. Third, chain coverage — this list alone spans Ethereum, Arbitrum, Base, Solana, TON, and Klever, and a 'universal' server is only as good as its support for the chain you actually use.

Star counts run lower in this category than elsewhere; several of the most production-oriented listings are zero-star hosted APIs rather than GitHub-famous repos. Judge by the listing's tool descriptions, not popularity alone.

Blockchain is the rare category where x402 adoption is visible in the listings themselves: Gas Oracle API, DEX Swap Quotes API, the Solana Priority Fee Estimator, and 2s-io MCP all describe themselves as x402 services, with calls settled in USDC. The fit is natural — an agent that needs one gas quote should pay for one gas quote, not a monthly data subscription. Per-call prices on Loomal start at $0.01, settlement lands on Base in about two seconds, and Loomal's 5% fee on settled transactions is currently waived.

All 27 live Blockchain listings: loomal.ai/marketplace?category=Blockchain.