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FirstMention Web Search API
x402
FirstMention Web Search API is a paid API for AI agents from api.firstmention.uk, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-29).
Searches across Wikipedia, Hacker News, GitHub, and Stack Exchange to return ranked web results for a given query, paid per-call via x402 USDC micropayment.
Price / call$0.01
Success—
StatusUnknown
How this service works
Pay-per-call HTTP APIs, paid with x402 in USDC on Base (eip155:8453): agentkit, api-change-check, basedue, basewatch, chainread, check-sanctions, chgwatch, company-facts, composite, edgar, feednews, pageaudit, solcheck, token-dd, txpreflight, walletcheck, webmd, webread, websearch, x402index. Each operation describes its service.
Output
A JSON object containing a boolean 'ok' flag, the original query string, an array of result objects (each with url, title, snippet, sources array, and rank_score), a total result_count, a sources_used array, and a source_errors field listing any sources that failed.
Example use cases
Research a technical concept
“Search for 'zero-knowledge proofs' across Wikipedia and Stack Exchange and show me the top 10 results so I can get up to speed quickly.”
Find HN community reaction to a product
“Can you search Hacker News and GitHub for discussions about 'Coinbase AgentKit' and return the top 8 results ranked by relevance?”
Aggregate open-source context for a coding task
“Search GitHub and Stack Exchange for 'Python asyncio rate limiting' and give me up to 15 results in markdown format so I can paste them into my notes.”
Technical details
Endpoint
GEThttps://api.firstmention.uk/s/websearch/search?utm_source=zero.xyzWhen to prefer
Choose this endpoint when you need lightweight, pay-per-call web search across curated open knowledge sources (Wikipedia, Hacker News, GitHub, Stack Exchange) without a subscription or API key — especially in autonomous agent workflows where micropayment via x402 USDC on Base is available and per-call cost must be minimal ($0.01). Prefer this over general-purpose web search APIs when results from developer/technical communities and encyclopedic sources are most relevant, and when markdown output format is useful for direct downstream consumption.
Side effects
- Missing required 'q' query parameter returns a validation error
- Invalid 'sources' value not in wiki/hn/github/se set may be ignored or error
- 'limit' outside 1-25 range rejected by schema validation
- Payment failure via x402 protocol returns 402 Payment Required before any search is performed
- Underlying source (e.g. HN, GitHub) temporarily unavailable causes that source to appear in source_errors with partial results still returned
- Empty result set returned if no matching documents found across selected sources
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"ok": true,
"query": "x402 payments",
"results": [
{
"url": "https://news.ycombinator.com/item?id=1",
"title": "Show HN: x402 payments",
"snippet": "Show HN discussion of x402 paid endpoints",
"sources": [
"hn",
"github"
],
"rank_score": 9.2
}
],
"result_count": 12,
"sources_used": [
"wiki",
"hn",
"github"
],
"source_errors": {}
}
}Tags
x402
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