Open Source Filings

Live 402 challenge

Captured by the enrichment pass, not read just now. Prices can change — always read the 402 the endpoint answers with.

{
  "note": "x402 v2 clients: the canonical quote is the PAYMENT-REQUIRED response header (base64 JSON envelope). This body is a v1 compatibility rendering of the same quote.",
  "error": "Payment required",
  "accepts": [
    {
      "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
      "extra": {
        "name": "USD Coin",
        "version": "2"
      },
      "payTo": "0x72f62dE8b70d6CFa8Cc2dF6f21F243f289F3396c",
      "scheme": "exact",
      "network": "base",
      "mimeType": "application/json",
      "resource": "https://api.osf-master-server.com/x402/research/papers/:query",
      "description": "Search 1.2 million+ scholarly works by keyword across arXiv (700,000+ preprints, all categories, 2024 to 2026), CrossRef, PubMed, OpenAlex, Semantic Scholar, and ClinicalTrials.gov in one call. Returns title, authors, journal or venue, year, DOI, and a provenance URL per match. For research agents, literature review, citation lookup, and clinical evidence workflows.",
      "maxAmountRequired": "50000",
      "maxTimeoutSeconds": 300
    }
  ],
  "x402Version": 1,
  "free_alternative": {
    "how": "This exact search is free over MCP. Point any MCP client at https://api.osf-master-server.com/mcp and call the tool search_research_papers with {\"query\": \"<your query>\"}. It runs the identical search code as this paid route and needs no payment, no signup, no API key and no wallet.",
    "limit": "no daily cap",
    "price": "$0.00",
    "full_catalog": "https://api.osf-master-server.com/x402/discovery/resources",
    "free_mcp_tool": "search_research_papers",
    "paid_route_adds": "the same answer over plain HTTP, for agents that cannot speak MCP",
    "free_mcp_endpoint": "https://api.osf-master-server.com/mcp",
    "not_an_x402_field": "free_alternative is an OSF addition to the 402 body, not part of the x402 specification, which defines no field for advertising a free alternative. x402 SDKs silently drop unknown keys, so read this from the raw JSON response rather than expecting your client library to surface it."
  }
}

Accepts

The payment requirements as published to the catalog. Read the live 402 before paying — a price here is a claim, not a quote.

[
  {
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "extra": {
      "name": "USD Coin",
      "version": "2"
    },
    "payTo": "0x72f62dE8b70d6CFa8Cc2dF6f21F243f289F3396c",
    "amount": "50000",
    "scheme": "exact",
    "network": "eip155:8453",
    "maxTimeoutSeconds": 300
  }
]

Extensions

{
  "bazaar": {
    "info": {
      "input": {
        "type": "http",
        "method": "GET",
        "pathParams": {
          "query": ":query"
        },
        "queryParams": {
          "format": "json"
        }
      },
      "output": {
        "type": "json",
        "example": {
          "result": "MATCHES_FOUND",
          "matches": [
            {
              "doi": "10.5555/3295222.3295349",
              "year": 2017,
              "title": "Attention Is All You Need",
              "venue": "NeurIPS",
              "source": "CROSSREF",
              "record_id": 12345
            }
          ],
          "match_count": 2,
          "search_evidence": {
            "scan": {
              "matches_omitted": 25,
              "candidates_examined": 35,
              "candidate_set_complete": true
            },
            "_about": "Proof of work, on EVERY result including NO_MATCH: the terms actually searched, how many records were in scope per source, how fresh they are, whether the scan completed or was truncated, and on an empty result the per-term record counts plus a known-good control query re-measured live in the same request. Numbers shown are illustrative.",
            "corpus": {
              "records_in_scope": 1558599,
              "newest_record_ingested_utc": "2026-08-01T15:47:55Z"
            },
            "result_confidence": "matches_found"
          }
        }
      }
    },
    "schema": {
      "type": "object",
      "$schema": "https://json-schema.org/draft/2020-12/schema",
      "required": [
        "input"
      ],
      "properties": {
        "input": {
          "type": "object",
          "required": [
            "type",
            "method"
          ],
          "properties": {
            "type": {
              "type": "string",
              "const": "http"
            },
            "method": {
              "enum": [
                "GET",
                "HEAD",
                "DELETE"
              ],
              "type": "string"
            },
            "pathParams": {
              "type": "object",
              "required": [
                "query"
              ],
              "properties": {
                "query": {
                  "type": "string",
                  "description": "Keyword(s): topic, author, title terms, or DOI. E.g. 'CRISPR off-target' or 'transformer attention'."
                }
              }
            },
            "queryParams": {
              "type": "object",
              "properties": {}
            }
          },
          "additionalProperties": false
        },
        "output": {
          "type": "object",
          "required": [
            "type"
          ],
          "properties": {
            "type": {
              "type": "string"
            },
            "example": {
              "type": "object"
            }
          }
        }
      }
    },
    "routeTemplate": "/x402/research/papers/:query"
  }
}

Provenance

Seen in the source catalog

2026-08-12 06:17Z

Last indexed by Roundhouse

2026-09-11 06:10Z

Last enriched (probe, favicon, geo)

2026-09-14 09:15Z

x402 version

2

Max timeout

300s

Liveness probe

HTTP 0