"Free PostgreSQL Database Solutions" matching MCP servers:

Enables retrieval of customer records and triggering refunds via MCP tools, supporting both stdio and streamable HTTP transports.

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.

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.

A template for building MCP servers with a built-in paywall gate that offers free local execution and premium server-side execution via Stripe and x402 payment lanes.

MCP server providing Polymarket weather-market bucket-transition signals for AI agents, with free city/signal inspection tools and paid signal bundles via USDC on Base using x402.

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).

Generate crypto QR codes (BTC, ETH, SOL, USDC, USDT, EURC) and manage payment sessions from Claude Desktop or any MCP client. Non-custodial, free.

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.

Payment firewall for AI agents: a signed, independently verifiable verdict on every money-moving action. Blocks wrong/lookalike payee, over-cap, and duplicate-invoice (BEC) fraud before money moves — anyone can verify a verdict against the public JWKS. Free, local-first, non-custodial.

Quote, book, and track real LTL, FTL, cargo van, and box-truck freight through the Warp network - 20 tools, in-chat login, Stripe-charged bookings, and real carrier dispatch. Quoting is keyless; booking needs a free Warp account with a card on file.

Discover and pay for APIs and MCP tools per call over Bitcoin Lightning (L402): search the bolthub marketplace, preview prices, and pay from your own wallet (LND, NWC, LNbits) with hard budgets, prepaid credit, scoped sub-agent delegation, and verifiable receipts. Non-custodial and works without a wallet for search and free tools.

MCP server for Sean-Claude Van Damme's General Store, enabling AI agents to browse and purchase digital goods and services using USDC payments over the x402 protocol.

Identity infrastructure for the agent economy. Mint an agent ~handle in two free calls with no human account, then verify anyone and read inferred traits under the consent the person set in advance.

MCP server for a live x402 payment gateway on Base (USDC). Lets AI agents discover, preview for free, then pay per call — with prepaid gasless payments, signed receipts, and delta delivery.

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.

Client-side MCP wrapper for Orisha Data's public x402 endpoints, providing free preview tools and paid market data access via x402 payments.

MCP server for the AI-agent economy: free Kazakhstan / Central-Asia utilities (Kazpost parcel tracking, IIN/BIN & IBAN validation, GLEIF LEI lookup, KZT/ECB FX rates, weather) callable with no account, plus per-call purchase of KYA-verified API listings governed by Regent Protocol.

Free, open-source (MIT), local-first Swiss accounting MCP server: an AI agent posts double-entry journal entries, categorises and chases invoices, and prepares the MWST-Abrechnung (the Swiss VAT return), with a minimalist Studio for human oversight. Posted entries are append-only and immutable, corrections are reversing entries, and every query is tenant-scoped.

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.