x402-research

Scholarly search over arXiv, Crossref, and Semantic Scholar — papers, citation graphs, formatted bibliographies. One HTTP call, $0.002 in USDC on Base or Solana, and the merged paper list comes back in the response body: titles, authors, venues, DOIs, abstracts, citation counts.

Docs site: https://nirholas.github.io/x402-research/

Why x402 for this

Literature search is exactly the workload API keys handle badly. An agent doing a review needs two hundred queries this afternoon and none next month, and the human who owns the key is not the one making the calls. With x402 the route quotes its own price in the 402 response, the agent pays $0.002 per query in USDC on whichever chain it holds funds on, and there is nothing to sign up for, leak, or rotate. All three upstreams are free and keyless — the price buys the merge, the de-duplication, and the ranking, not a resold subscription.

Quickstart

git clone https://github.com/nirholas/x402-research
cd x402-research
npm install
npm run dev            # http://localhost:4021 — no configuration needed

See the price with no wallet at all:

curl -s "http://localhost:4021/search?q=attention%20is%20all%20you%20need&limit=5" | jq
# 402 + accepts: [ USDC on Base, USDC on Solana ]

Then buy it, from an agent (wallet funded with Base Sepolia USDC — https://faucet.circle.com):

PRIVATE_KEY=0xYourTestKey npm run client

API

Route	Price	What you get back
GET /search	$0.002	Merged, de-duplicated, citation-ranked papers with authors, venue, DOI, abstract, and citation count, plus a per-source status block
GET /paper/:id	$0.003	Full metadata, abstract, TL;DR, open-access PDF link, plus the top citing works and the reference list
POST /bibliography	$0.005	Paste-ready BibTeX and/or APA 7 references, one entry per DOI
GET /	free	Service metadata, live prices, active payment rails, upstream list
GET /health	free	Liveness probe
GET /.well-known/x402	free	Machine-readable discovery manifest
GET /skill.md	free	This agent skill card
GET /openapi.json	free	OpenAPI 3.1 spec

Full reference: docs/api.md · openapi.json

How x402 works

Pay in USDC on Base or Solana — your client picks the rail.

1. 402 — the route, called without payment, replies HTTP 402 with an accepts array holding both rails: exact price ($0.002 → 2000 USDC base units), asset, and payTo.
2. Sign — on Base, the client signs an EIP-3009 USDC authorization (no gas from the payer). On Solana, it signs an SPL transferChecked whose fee payer is the facilitator's sponsor account (so the buyer needs USDC only, no SOL).
3. Settle — the server hands the payload to the facilitator (https://x402.org/facilitator), which verifies and settles on the chosen chain.
4. 200 — the same request returns the artifact in the body, with the settlement receipt in the X-PAYMENT-RESPONSE header.

Rail	Network	Asset	payTo
EVM	base-sepolia (base on mainnet)	USDC	0x40252CFDF8B20Ed757D61ff157719F33Ec332402
Solana	solana (solana-devnet on devnet)	USDC	WwwuGbqHrwF5RG89KhUbmRWEvjnRH9k5kVM5p7T3WwW

Those are the suite's public receive addresses and the server's defaults. Set PAY_TO_ADDRESS / SOLANA_PAY_TO_ADDRESS to be paid yourself.

Walkthroughs: examples/curl.md · examples/agent-client.ts · docs/tutorial.md

Real backend / API keys

Env	Effect
(nothing)	All three sources are keyless and are called live out of the box. npm install && npm run dev talks to real arXiv, Crossref, and Semantic Scholar.
CONTACT_EMAIL	Goes into the outgoing User-Agent, which puts you in Crossref's "polite" pool — faster and more reliable than the anonymous lane.
S2_API_KEY	Optional Semantic Scholar key for higher rate limits. Without it the anonymous lane is used and a 429 shows up as "semanticScholar": "rate-limited" in the sources block instead of an error.

All variables: .env.example

For AI agents

• skill.md — agent-facing skill file: endpoints, prices, schemas, both payment rails. Point your agent at it.
• GET /.well-known/x402 — discovery manifest listing every resource with both networks. Indexable by x402scan.com, the x402 Bazaar, and agentic.market.
• MCP — examples/mcp-tool.md exposes these routes as Claude MCP tools, with per-wallet spend caps and a claude_desktop_config.json example.
• More: docs/agents.md

Docs

• Landing: https://nirholas.github.io/x402-research/
• Tutorial · API reference · For AI agents

Support

Questions, bugs, or a listing request: nichxbt@gmail.com · open an issue

License

Apache-2.0. Part of the x402 Suite.

Star History

Support the project

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Built for AI agents too

Coding agents and LLM tooling can read this repo directly: AGENTS.md, llms.txt, llms-full.txt. Point an agent at https://github.com/nirholas/x402-research and it has the context it needs.

More from the same author

• All repositories by nirholas: the full catalog, grouped by topic
• three.ws: the platform for 3D AI agents with Solana wallets, a skill marketplace and x402 payments
• Questions or ideas: open an issue or start a discussion

Contributors