"Services or tools available for free without requiring an API key" matching MCP servers:

Free DEX aggregator API that returns executable swap calldata across 46 EVM chains. No API key required. Single GET request returns ready-to-sign transactions for any token pair.

An MCP server that enables fee-free USDC transfers on the Base blockchain network using Coinbase CDP MPC Wallet integration, with support for ENS and BaseName domain resolution.

MCP server providing real-time crypto prices (Chainlink + Binance), Polymarket prediction market data, deep web research, and JS-rendered web scraping. All services available via x402 Solana micropayments.

Enables agents to access production-grade paid MCP tools with real on-chain x402 v2 settlement, including EVM wallet risk scoring, payload normalization, and facilitator discovery, all discoverable via Bazaar-compatible metadata.

Pay-per-use AI security and research tools for autonomous agents on Base, enabling honeypot detection, risk assessment, wallet analysis, and yield optimization via the x402 protocol.

Real-time crypto, stock, and prediction-market data for agents — prices, indicators, funding rates, DeFi TVL, macro calendar, and an AI momentum score. Configure one Base wallet key and it just works. No signup, no dashboard, no subscription.

Bitcoin data for AI agents. Pay-per-query via x402 micropayments. No API keys. No subscriptions. No tokens.

55+ pay-per-call tools for AI agents over MCP: live telemetry, blockchain/on-chain checks, environmental, transit, finance, and network utilities. No API key or signup — agents pay per request with x402 USDC micropayments (Base and Solana).

Provides access to measured x402 ecosystem data, allowing users to query which merchants actually accept payment (verified by real on-chain settlements) and explore market concentration and health statistics.

Enables natural language interaction with the Avalanche blockchain through AI assistants, allowing users to execute Avalanche CLI commands and AvalancheJS API operations without technical knowledge.

MCP server for pay-per-call DeFi and crypto data via x402 micropayments on Base. 8 endpoints: token prices, TVL, funding rates, token security, gas tracker, whale monitoring, wallet profiling, and yield scanning.

Non-custodial crypto swaps for AI agents: Solana (Jupiter) + 7 EVM chains (KyberSwap), 1288+ assets, cross-chain routing, priority-fee oracle, Hyperliquid perps. Returns unsigned transactions — your wallet signs, no API key, no KYC. Hosted at https://swaptitan.net/mcp

Enables interaction with lightning addresses and common lightning tools via your LLM, providing Lightning Network functionality through natural language.

23 tools for AI agents working with Nostr Open source. No API key. No account. NIP-46 remote signing Publish notes, reply, react, repost Encrypted DMs (NIP-04 + NIP-44) Fetch events, profiles, social graph

A comprehensive toolkit for Ethereum blockchain analysis within Claude AI, enabling contract auditing, wallet analysis, profitability tracking, and on-chain data retrieval.

Enables MCP clients to use paid tools for secret scanning, agent-config auditing, and OG image rendering, with payments handled over the x402 protocol on Base.

MCP server for cross-chain bridging, enabling AI agents to find routes, estimate costs, check risks, execute transfers, and track status across blockchains.

43 x402-enabled API tools — DeFi, wallet security, AI/ML, developer tools, SEO. Pay-per-call USDC on Base via x402 protocol.

MCP server for managing TON blockchain sites, deployments, DNS, and storage via the Resistance Tools platform.

An MCP server that enables LLMs to query DAOs, proposals, and voting data from Tally's blockchain governance API across multiple networks.