"Free and open-source coding assistants" matching MCP servers:

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.

This MCP wraps Bitrefill public API to allow agents to search for products and shop using cryptocurrencies like Bitcoin, Ethereum, Solana, and many more.

A Node.js service that provides spot trading functionality through the LnExchange API.

Wallet-funded MCP client for six paid Utilia tools: Solana priority fees, transaction diagnosis and simulation, token-risk checks, PDF-to-Markdown, and audio normalization over x402. MIT-licensed and installable from npm.

Exposes fourteen read-only tools over the HEY Research public API, letting assistants look up Robinhood Chain projects, builders, shipped work, relationships and market context, with each answer tagged FACT, DERIVED or UNKNOWN and unmeasured fields omitted rather than zeroed. Runs over stdio or hosted Streamable HTTP, and gives no trade instructions.

Enables AI agents to securely use Open Agent ID credentials for signing requests, looking up agent data, and exchanging encrypted messages. It performs all cryptographic operations within the server process to ensure private keys are never exposed to the AI agent.

Non-custodial x402 MCP payment layer for AI agents — the open-source alternative to Vercel x402-mcp

Enables AI coding assistants and trading bots to verify smart contracts, test honeypot traps, assess DEX liquidity, and check wallet counterparty risk before deploying or trading capital on Base. It exposes preflight clearance, token audits, KYA reputation, and web-scraping tools with free and paid x402 tiers.

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

MCP services for agent security preflight, source scanning, injection screening, proof-of-work policy rehearsal, carbon accounting, climate disclosure and regulatory monitoring. Use each hosted endpoint in the README. Inspect a free quote before buyer-authorized x402/USDC payment. Includes free trust and settlement tools. Maxwell rehearsal does not activate runtime protection.

An MCP server that records consented, attributed, paid-for receipts for open-source dependencies, settling per-call USDC payments on Algorand with on-chain attribution.

A paid callable research agent that provides source-backed reports, onchain intelligence, and claim verification via MCP tools for coding tools like Codex, Claude Code, Cursor, and Windsurf.

Enables AI assistants to access Solana/Pump.fun tools, unsigned transaction tickets, Open Wallet Standard public wallet operations, and OpenRouter/RedPill model routing.

CheapestInference — unlimited flat-rate API for frontier open-source LLMs

An official Model Context Protocol (MCP) server that provides AI agents with native, real-time access to high-value developer datasets. Currently supports SaaS/AI pricing comparisons, trending developer discussions (V2EX), and real-time Base/Arbitrum gas rates. Free Open Beta is active.

MCP server for Chainlink Runtime Environment, enabling build, simulate, deploy, and manage CRE workflows from any MCP client.

Checks live x402 routes across Base, Solana, and Algorand before agents spend. $0.003 USDC settles only for a valid live eligible route; normal typed misses are not settled. Free preview and validate tools. Seller payment is separate; the agent keeps its wallet. Optional signed route-binding receipts support buyer-side checks.

Provides read-only tools to query live Polymarket prediction-market data via the public Gamma API, enabling search, browsing, and detailed market and event information.

Rug pull risk scores and on-chain forensics for memecoins on Solana, Ethereum, Base and Robinhood Chain - launch-bundle detection, funding-origin tracing, deployer history, insider networks and whale flow. 15 read-only tools.

Read-only on-chain query surface for the AgentCivics civil registry on Sui — soulbound AI-agent identities, on-chain memories, reputation, refusal records. Hosted, no install, no keypair. For write tools (register, write_memory, record_refusal), install the npm package @agentcivics/mcp-server locally and supply your own keypair.