How to pay for Recall Kitchen MCP tools with x402

Recall Kitchen's MCP server now lets AI agents pay per call for recall lookups using x402, charging $0.025 in USDC on Base once an anonymous IP quota of 5 searches per hour and 15 per day is exhausted, with photo search always requiring payment or an API key. The server returns an HTTP 200 JSON-RPC result carrying an x402 Payment Required challenge rather than a bare HTTP 402, and publishes its price and pay-to address at a .well-known/x402 endpoint. Account tools such as watches and inventory do not accept x402 and require a free API key.

Recall Kitchen's MCP server lets AI agents look up government-published product, food, vehicle and drug recalls. Most lookups are free; past the free quota and for photo search an agent can pay per call with x402 in USDC on Base. Here's exactly how. Disclosure: I build Recall Kitchen. Docs: https://recallkitchen.com/docs?utm source=devto&utm campaign=x402 howto https://recallkitchen.com/docs?utm source=devto&utm campaign=x402 howto You don't need an account to keep using the server. A few anonymous searches per IP are free 5 an hour, 15 a day , and photo search is never in that free quota. After the quota, an x402-capable client can pay per call: $0.025 in USDC on Base. When a call needs payment, the server returns a normal JSON-RPC result whose content is an x402 "Payment Required" challenge HTTP 200, isError: true , not a bare HTTP 402. Your client pays it and retries. The price and pay-to address are published at https://app.recallkitchen.com/.well-known/x402 https://app.recallkitchen.com/.well-known/x402?utm source=devto&utm campaign=x402 howto . x402 covers search and photo search only. Account tools like watches and inventory need a free API key instead. The full rules are in the docs https://recallkitchen.com/docs?utm source=devto&utm campaign=x402 howto and the API Terms https://recallkitchen.com/api-terms?utm source=devto&utm campaign=x402 howto x402 . POST https://app.recallkitchen.com/mcp https://app.recallkitchen.com/.well-known/x402 | Tool | Free anonymous quota | x402 / API key | |---|---|---| | search product recalls and other non-photo search tools | Yes — a few calls per IP docs/API terms: 5/hour, 15/day | After the IP quota, pay with x402 or send an API key | | search product recalls from image photo, beta | No — never in the free anonymous quota | Always needs an API key or x402 | Account tools watches, inventory, notifications, key management do not accept x402; use a free API key from signup / Integrations. For MCP tool calls that require payment, the server answers HTTP 200 with a JSON-RPC tools/call result whose content is an x402 Payment Required payload isError: true . That HTTP 200 + JSON-RPC payment challenge is correct for this MCP integration — clients should not expect a bare HTTP 402 on the MCP POST for tool payment. Live example image search, unpaid , truncated: { "jsonrpc": "2.0", "id": 2, "result": { "isError": true, "structuredContent": { "error": "Payment Required", "x402Version": 2, "accepts": { "scheme": "exact", "network": "eip155:8453", "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913", "amount": "25000", "payTo": "0x8E2d8e2850Baf623A8A886DE7c80CDfB83a5cfa3", "maxTimeoutSeconds": 60, "extra": { "name": "USD Coin", "version": "2" } } , "resource": { "url": "mcp://tool/search product recalls from image", "description": "Photo beta : identify products in an image URL, data URI, or MCP image content", "mimeType": "application/json" } } } } amount is USDC atomic units 6 decimals : "25000" = $0.025 . The well-known document publishes the same price as decimal "0.025" . From /.well-known/x402 and the live challenge they match : | Field | Value | |---|---| | Network | Base mainnet — eip155:8453 | | Asset | USDC on Base — 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 | | Currency | USDC | | Price | $0.025 per call unless a live challenge states otherwise | | Pay to | 0x8E2d8e2850Baf623A8A886DE7c80CDfB83a5cfa3 | | Scheme | exact | | x402 version | 2 | Do not invent other prices; always prefer the live accepts on the challenge. https://app.recallkitchen.com/mcp streamable HTTP / JSON-RPC . Prefer a free API key X-API-Key: rk ... for Grok, or Authorization: Bearer rk ... for Claude/Cursor when you have one — that skips x402 for search tools. search product recalls after the free IP quota, or search product recalls from image any time without a key . accepts 0 network, asset, amount, payTo . X402 EVM PRIVATE KEY and registers scheme eip155:8453 , sign and settle the payTo for amount atomic units on Base. export X402 EVM PRIVATE KEY=0x... Base wallet funded with USDC + gas cd examples/go go run ./search product recalls -query spinach -location Iowa Or set RK API KEY / RECALL KITCHEN API KEY instead of paying per call. GET https://app.recallkitchen.com/.well-known/x402 tools/call → /mcp HTTP 200 + Payment Required JSON-RPC