research by fourzerotwo

Search works

Bibliographic search across Crossref works.

Search works Free

Bibliographic search across Crossref works.

cost: Free then $0.003 / call
MCP tool: crossref__search
method: GET

Free up to 50 calls a day over MCP (500 with a free key), then $0.003 per call by card credit or USDC. Free key · Pay by card

GET https://fourzerotwo.si/v1/crossref/search

Param	Type	Description
q	string	Query

# free: send a free key from https://fourzerotwo.si/free
curl -H "X-API-Key: fzt_…" "https://fourzerotwo.si/v1/crossref/search?q=deep%20learning%20review"

# no key: returns 402 with the price, for x402 agents
curl -i "https://fourzerotwo.si/v1/crossref/search?q=deep%20learning%20review"

by fourzerotwo

Report this endpoint

Use it from an AI agent (MCP)

Add the server once, then ask for this data in plain English. The agent finds the endpoint with search_apis and runs it with call_api.

{
  "mcpServers": {
    "fourzerotwo": { "type": "http", "url": "https://fourzerotwo.si/mcp" }
  }
}

# the call the agent makes
call_api {"tool": "crossref__search", "arguments": {"q":"deep learning review"}}

Search works

Search works Free

Use it from an AI agent (MCP)

More from Crossref DOI Metadata