"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.

Model Context Protocol (MCP) server providing real-time institutional Spot Bitcoin (BTC) and Ethereum (ETH) daily net flow metrics for AI agents.

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.

An unofficial, read-only MCP server for Sarwa Odyssey that provides portfolio, holdings, transactions, watchlists, and agent snapshots via deterministic JSON documents.

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.

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

MCP server for querying cryptocurrency portfolio data, transaction history, net worth, and historical snapshots across 20+ blockchains via the Octav API.

Pay-per-call tools for AI agents including trust checks, due diligence, market data, and human-verified approvals, settled in USDC on Base via the x402 protocol.

Enables interactive access to TradeSearcher strategies and backtests via CLI and MCP, allowing agents to search, backtest, and compare trading strategies.

A collection of three zero-dependency MCP servers for web scraping via Chrome DevTools Protocol, crypto wallet and price monitoring, and email validation with SMTP sending.

Enables AI assistants to query blockchain chain data, including chain details, RPC endpoints, and chain relationships, through a Model Context Protocol server.

Provides 63 production-ready API tools for AI agents, including web scraping, AI generation, crypto data, OCR, image generation, audio transcription, text-to-speech, email, and domain lookup.

Enables AI agents to inspect the public NFH protocol corpus, verify census status, and prepare bounded Ethereum wallet intents for claims and non-custodial market actions while never signing or submitting transactions.

pay-per-call x402 API endpoints as MCP tools — web search, page-to-markdown, PDF extract, JSON repair/validate, crypto price, weather, IP geo, DNS, markdown lint + 20 agent-commerce aliases. Each tool proxies to vibes-coded.com and settles via x402 (USDC/Solana). Free-trial endpoints need no auth; paid ones need an x402 signature. Catalog is fetched live, so new endpoints appear automatically.

Real-time OFAC and global sanctions screening for AI agents: screen crypto addresses, emails, websites, government IDs, and countries against OFAC SDN and 10+ sanctions/crime/risk lists, plus PEP screening, VPN detection, and IP geolocation. Hosted remote streamable-HTTP server at https://api.compliapi.com/mcp (anonymous tools/list; free API key or x402 pay-per-call).

Enables AI agents to fetch real-time trading signals and technical indicators for cryptocurrencies using Binance market data.

A Node.js Express server that provides access to CoinGecko's cryptocurrency data through a comprehensive API interface, supporting both free and Pro APIs with automatic fallback functionality.