"A tool for finding academic papers using semantic search and citation analysis" 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.

Credit and payments for AI agent developers — over MCP. No crypto required

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

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.

Official Dodo Payments MCP servers - dodopayments-api for live payments, subscriptions, customers, products, refunds, license keys, and usage-based billing (browser OAuth, no API key needed) and dodo-knowledge for semantic search over Dodo Payments documentation.

x402-trust gives AI agents a "check before you pay" layer for the x402 ecosystem.

Create free, no-signup invoices from your AI assistant — the create_invoice tool returns a link that opens blankinvoicemaker.com pre-filled, ready to download as a watermark-free PDF.

MCP server for real FDM 3D-printing slicing, quoting, and design-for-manufacturability analysis via the FabTally API, supporting 12 printer profiles and 12 materials. Includes free discovery/printability tools and paid slice/quote/orientation tools settled via x402 (USDC on Base).

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

Enables individual proprietors and freelancers to manage daily accounting tasks like journal entries, invoice creation, and monthly reconciliation through simple tool calls, using freee's API.

Enables AI agents to search, license, and pay for rights-clean music per use, returning a verifiable license certificate.

agenticpay lets MCP server developers monetize tools via per-call USDC micropayments on Solana, using the x402 protocol. Each tool declares a price; agents pay via signed Solana transactions; settlement happens on-chain in ~1.5–2 seconds.

Generic Lightning-paywall sidecar that wraps any stdio MCP server and requires a paid Lightning invoice (via NWC) before forwarding priced tool calls. Per-tool prices are set via env; includes payment verification, replay protection, and an audit log — the upstream server stays untouched.

Pay per MCP tool call in USDC on Base. Non-custodial settlement, no admin keys, 30 bps fee.

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 existing MCP clients to access paid MCP servers by signing x402 payments locally and proxying tool calls, with automatic line management, retries, and spend limits.

Integrates PayU payment services with AI tools through the Model Context Protocol, enabling payment link creation, transaction retrieval, and settlement analysis.

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.