"Free Graph and Network Visualization Tools (No API Key Required)" matching MCP servers:

Enables agents to call paid utilities for DNS/SSL checks, site status, summarization, keyphrase extraction, decision advice, data cleanup, claim verification, and grounding via per-call USDC payments over x402, with free discovery tools and no signup or API key.

Enables AI agents to discover, pay for, and retrieve receipts for external APIs via USDC micropayments through the SynapseNetwork Gateway, supporting stdio and Remote MCP.

Provides current weather conditions and 7-day forecasts for any location worldwide, covering temperature, humidity, wind, and precipitation, with pay-per-call micropayments via x402.

MCP server for Brazilian data lookups (Pix codes, CEP, CNPJ) and web rendering tasks (Markdown, screenshots, PDFs) via a paid HTTP API with x402 billing.

MCP server for deterministic financial transactions, providing tools to fetch account balances, check blocked PIX keys, and execute atomic PIX transfers with integer-cent precision.

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

MCP Server for the LINE Shopping API, enabling AI agents and tools to interact with LINE Shopping data and operations via the Model Context Protocol.

Kill switch + spend guard for AI agents that spend money: one policy, one sub-second freeze, and one signed audit ledger across every wallet vendor at once (Coinbase, Turnkey, Openfort + cards). Tools include a pre-flight request_spend guard, freeze, apply_policy, ledger, and x402/AP2 payment-mandate guards — free self-serve key, no account.

A comprehensive Model Context Protocol (MCP) server that provides complete access to the Recharge Storefront API endpoints. Enables AI assistants to manage subscriptions, customers, orders, and billing through a standardized interface.

Lets agents discover and health-check a directory of live x402 pay-per-call endpoints, probe an individual URL with one unpaid request to see whether it returns a payment challenge and at what price, and read on-chain settlement demand for crawled sellers. It also serves reproducible, solver-verified sudoku puzzles and the pricing, network, and payment details of the studio's paid pay-per-call routes.

MCP server for decoding and inspecting x402 payment headers and requests. Remote endpoint: https://lumenworks-x402-decoder.onrender.com/mcp

A Model Context Protocol (MCP) server that provides testing and debugging tools for Stripe integrations, including test clock management, customer and product management, and subscription testing.

An MCP server for Nexi POS payment operations, enabling creation of purchases and refunds, polling payment states, confirming transactions, and recovering unconfirmed transactions.

Discover audio and LLM services, compare seven voices, and check prices for free. Generate speech, transcribe audio and request LLM text with optional capped USDC payments on Base; voice-cloning requirements are also available.

Provides AI agents with SSRF-protected URL intelligence and 32 paid REST/MCP tools, plus a free catalog search, with payments in USDC on Base Mainnet.

Enables AI agents and scripts to manage bookings, provider assignment, rescheduling, cancellations, customers, quotes, invoices, and dashboard data through a self-hosted API and MCP interface using your own Chrome session.

Enables MCP clients to browse and purchase agent packages and pay per call for model inference on Robinhood Chain using USDG, with no account or API key required.

A local MCP server providing payment validation tools and resources, including card number Luhn checks, card network detection, and IBAN validation, with no network calls required.

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

Connects AI assistants to Quaderno's tax compliance engine, enabling tax calculation, tax ID validation, and invoice creation via natural language.