DopamineDesk x402 Marketplace MCP Server is an open-source MCP buyer adapter and marketplace client that enables machine-to-machine reports to be paid for per request, with payment completed through the x402 payment protocol on Base mainnet. It is aimed at scenarios that need to instantly purchase a current answer within a single workflow: no API keys, no account, no subscription, just buy a current result once with USDC when needed.
Purpose It packages multiple decision-ready data APIs into a marketplace callable through MCP, for existing agents to purchase per use when needed. The catalog includes agent-ready audits, vendor onboarding risk, transaction preflight, real-time x402 opportunity research, company intelligence, endpoint validation, website due diligence, VIN safety, market checks, security research, and atomic EVM reads.
Key capabilities Every billed route accepts ?preview=true. A preview is a live contract proof that shows the source, freshness, required inputs, and response structure, but intentionally hides the decision-ready values that only a paid call provides, so buyers can inspect the contract before paying.
How to use Start with the free find_marketplace_products MCP tool: provide the buyer task in natural language, and it returns three ranked live products plus a recommended_purchase containing the exact price, required inputs, and ready-to-use preview and paid-call payloads. Replace the example inputs with the buyer's real values, preview first if available, and execute the paid call only after the user authorizes the listed price and payment method.
The server can be used from any stdio-compatible MCP client, and its official MCP registry name is io.github.jblaz6335/ai-data-marketplace. The tool list is built from the production OpenAPI document; counts, prices, availability, data schemas, and source claims all come from the live contract rather than a hand-written endpoint list.
For existing agents, setting X402_TOOL_MODE=compact exposes only find_marketplace_products and purchase_marketplace_product; all live products remain available through these two tools. The default full mode retains product-specific tools to support existing integrations. Starting the default server does not require environment variables or a wallet key; a wallet is required only when the buyer chooses local-signature auto-pay. Remote The /mcp URL is a separately authenticated publisher integration, not the public stdio installation URL.
examples/README.md provides configuration that can be copied directly and a free end-to-end client check that discovers real products and requests their free previews, but never signs or submits payment. llms-install.md provides automated client installation instructions, whose default configuration exposes free discovery and previews without collecting wallet keys or enabling automatic payment.
Payment Method Every billed product uses x402 v2 exact payment on Base mainnet through the Coinbase CDP facilitator: call the endpoint and read the base64 PAYMENT-REQUIRED response header; sign the exact authorization with a compatible x402 buyer client; retry with PAYMENT-SIGNATURE; read the settlement details from PAYMENT-RESPONSE. PAYMENT_FLOW.md documents the manual and legacy confirmed-transaction paths.
Optional one-call purchase: the current npm release can automatically complete the x402 challenge, authorization, retry, and settlement. Install the public package directly; the buyer key stays local within the MCP process and is never sent to the marketplace; use a dedicated low-balance Base wallet rather than the main wallet. Set auto_pay: true when calling a product; the adapter rejects disabled, conflicting, invalid, or over-limit purchases and never falls back to uncapped payment.
Purchases can also be made with credits without configuring a wallet: the service is listed in APIHub's external x402 directory, and buyers with APIHub credits can have their agent sign and settle a single marketplace call without keeping a Base wallet or gas in the calling process. APIHub is an independent third party with its own account, credits, markup, and terms. Direct x402 remains the self-hosted path. Both paths settle the protected endpoint before delivering the paid result.
Use Cases and Limitations Suitable for MCP agent workflows that need decision-ready reports on a per-call basis, especially transaction pre-checks, company intelligence, endpoint validation, VIN safety, and marketplace checks. Limitations and caveats include: automatic purchases are optional, locally signed, and protected by a hard per-call cap; conflicting, malformed, disabled, and over-limit payment attempts fail closed; settlement details remain in the delivered result for reconciliation. A dedicated low-balance wallet should be used when using automatic payment. Production contracts, OpenAPI, Postman, LLM manifest, x402 manifest, etc. are located under the corresponding paths at ai-data-marketplace-1042299154756.us-central1.run.app. The project uses the MIT license.
