"An introduction to GraphQL or resources for learning GraphQL" matching MCP servers:

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.

Lets MCP-capable AI assistants interact with the Clockbook freelance marketplace through GraphQL, covering talent search, job postings, proposals, contracts, milestones and escrow, wallet, messaging, and notifications.

Provides 54 tools across 10 categories for Wave Accounting, enabling invoicing, customer management, products, transactions, bills, estimates, taxes, businesses, and financial reporting through Wave's GraphQL API.

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.

Enables AI agents to call paid APIs and settle HTTP 402 payment challenges with USDC on Base, without private keys ever being involved.

Keyless crypto payments for AI agents. One MCP call turns any wallet address into a non-custodial crypto payment link or tip jar, no API key and no account, with funds settling straight to your wallet at a 0% platform fee (USDC/USDT, BTC, LTC, DASH, DOGE, ZCASH).

An MCP server that wraps the Check Payroll API, providing 263 tools for managing companies, employees, contractors, payrolls, tax configuration, and more.

Keyless MCP exchanger for AI agents — pay an exact amount to one deposit address, EMC delivered to any address. USDT(Tron) > EMC. Live at https://swap.emercoin.com/mcp

An MCP server for the SmartBill Cloud API. It lets an MCP client issue and manage Romanian invoices, proformas and payments, download document PDFs, and read VAT rates, series and stock levels.

MCP server that lets a chatbot browse eSIM plans, sign in, prepare quotes, and execute wallet or card purchases on an existing eSIM platform, with safe typed tools.

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.

Enables agents and developers to check x402 endpoints, assess scores and wallet risks, authorize payments with spending rules, and report outcomes before an agent pays.

Universal x402 buyer agent — discover, pay for, and call any x402 paid API endpoint from Claude Desktop, Cursor, or Claude Code with automatic USDC payment via AgentCash.

MCP server that gates API calls to AI agents using proof-of-work (free) or Lightning payment (3 sats), providing challenge, verify, and status tools for per-call authentication without accounts.

MCP server for NovaPay that enables AI agents to create payment links, poll payment status, manage session lifecycle, and generate merchant keys.

Hand a secret to another agent as an encrypted, pay-per-read token delivered exactly once, leaving no copy behind. Also pre-flights an x402 endpoint before your agent pays it. Runs locally over stdio and encrypts in your own process, so there is no hosted version to hand your plaintext to.

An MCP server that exposes the pacs008 ISO 20022 FI-to-FI Customer Credit Transfer library as tools for AI agents and assistants, enabling generation, validation, and parsing of pacs.008 credit transfer XML messages.

Unified gateway for ISO 20022 message families, providing meta-tools to search, describe, validate, generate, and parse financial messages.

Enables MCP-wired agents to fetch live, historical, or proof-backed Base-mainnet asset prices signed with ML-DSA-65 and anchored to Hedera, automatically handling x402 USDC payments; it also lists the provider's available x402 services.