"How to search for academic papers using Google Scholar" matching MCP servers:

Pay-per-use semantic web search for AI agents. Powered by SearxNG, agents pay in sats via Lightning Network micropayments — no API keys required.

Pay-per-call USDC payment proxy for AI agents. Issue scoped Pay Tokens with hard spending caps and auto-journal every charge to freee / Money Forward / QuickBooks.

Provides a three-layer payment firewall for AI agents, enabling identity verification, risk screening, and execution authorization with on-chain policy enforcement for secure and auditable transactions.

Free x402 endpoint checker plus paid report and metadata tools. Remote MCP server for agents. Written by AI named Nock, not a human.

Connects Claude to the customer side of Housecall Pro, letting you view estimates and invoices, check company details, and decline estimate options using the link your contractor sent.

Enables MCP clients to access Monobank's open API for exchange rates, account and jar balances, and statements, as well as set webhooks, using natural language tools.

Enables AI agents to discover, inspect, and pay for paid HTTP and MCP services using USDC on Solana with a self-custodial wallet.

Enables AI agents to discover, evaluate, and purchase live data from the Macaroon Network marketplace using semantic search, metadata checks, and Bitcoin Lightning payments.

Enables AI agents to spend with the user's own key by paying via USDT TRC-20 and buying Visa/Mastercard prepaid cards, travel eSIMs, and gift cards, and also provides access to policy and how-to documentation.

MCP server for Pine Labs payment gateway that connects AI assistants to Pine Labs payment APIs using client credentials.

Enables AI agents to generate static Pix QR codes for Brazilian payments using natural language, with EMV 4.0 compliance and no external API required.

Enables AI agents to discover and call MoiPayWay API endpoints using a merchant API key, with tools for wallets, transfers, collections, cards, users, verification, and webhook signature validation.

MCP server to connect AI assistants to the AdvinPay payment API, enabling PIX charges, transaction queries, and documentation search.

Enables autonomous agents to calculate deterministic profit and loss, attribute revenue and costs, and generate signed operational reports using x402 micropayments.

Enables AI agents to discover, query, and pay for HTTP endpoints and MCP tools using Stellar USDC/SEP-41 stablecoins through a federated P2P bazaar catalog and x402 payment facilitator.

Enables AI agents to autonomously pay for and discover services using HPP USDC.e over the x402 protocol, without API keys or manual signing.

An MCP server that enables AI agents to search, pay for, and call paid APIs using the x402 protocol, with automatic USDC settlement.

MCP server for the x402 micropayment marketplace minia2a.uk, enabling AI agents to discover, call, and pay for 1,700+ services using USDC micropayments with no API keys or subscriptions. Supports registration, credits, service browsing, and autonomous calling with Claude Code auto-mode.

Enables users to connect bank accounts within a chat session using Sophtron's UCW widget and query account information, owner details, and transactions persistently.

MCP server that allows AI agents to discover and pay for thousands of APIs (x402 on Solana/Base) using a single key, with automatic payment handling and a federated catalog of machine-payable endpoints.