NCBI E-utilities

PubMed and Entrez database search via eutils.ncbi.nlm.nih.gov. Keyless with 3 req/s courtesy limit. Machine-payable per request.

Robinhood Chain

Offers

Offer	Endpoint	Price
PubMed search Searches PubMed. Requires ?db=pubmed&term= plus &retmode=json (e.g. ?db=pubmed&term=crispr&retmode=json). Returns matching PMIDs.	`/m/ncbi-eutils/esearch`	0.006 USDG

Machine-readable: openapi.json with x-payment-info offers.

Try it live

Run the full MPP flow from your browser: catch the 402, sign the payment with your wallet, and watch it settle on-chain.

Pay with an agent

Any MPP or x402-compatible client works. With mppx, payment is automatic:

// x402 exact scheme (permit2) on Robinhood Chain
// 1. GET the endpoint, read the payment-required header (base64 JSON)
// 2. Sign PermitWitnessTransferFrom against Permit2 for the advertised offer
//    (spender = x402ExactPermit2Proxy, witness.to = merchant wallet)
// 3. Retry with the payment-signature header; settlement tx arrives
//    in the payment-response header
const res = await fetch('https://api.meshgateway.co/m/ncbi-eutils/esearch', {
  headers: { 'payment-signature': signedPaymentPayload },
})

Or inspect the challenge yourself:

curl -i https://api.meshgateway.co/m/ncbi-eutils/esearch
# HTTP/1.1 402 Payment Required
# WWW-Authenticate: Payment id="…", method="evm", intent="charge", …