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The world's knowledge, one API call away.

Book402 is an AI-native book knowledge API. Search 3,807 books, get summaries, and discover connections — all via a simple REST API. AI agents pay per query with USDC on Base using the x402 protocol.

Why Book402?¶

Feature	Description
:books: 3,807 Books	Curated library spanning psychology, philosophy, business, science, and more
:mag: Hybrid Search	BM25 keyword + vector semantic search for high-quality results
:coin: Pay-per-query	Micropayments via USDC on Base — $0.01 per search, $0.05 per summary
:key: No API keys	Uses HTTP 402 + x402 protocol — your wallet IS your authentication
:robot: Agent-native	Built for AI agents, MCP servers, and autonomous workflows

How It Works¶

sequenceDiagram participant Agent as AI Agent participant API as Book402 API participant Facilitator as x402 Facilitator participant Chain as Base (L2) Agent->>API: GET /search/hybrid?q=stoicism API-->>Agent: 402 Payment Required + PAYMENT-REQUIRED header Note over Agent: Signs USDC transfer (EIP-3009) Agent->>API: GET /search/hybrid?q=stoicism + X-PAYMENT header API->>Facilitator: Verify payment signature Facilitator-->>API: ✅ Valid API-->>Agent: 200 OK + search results API->>Facilitator: Settle payment Facilitator->>Chain: Submit USDC transfer on-chain Chain-->>Facilitator: ✅ Settled

Quick Example¶

# Free — browse books
curl https://book402.com/books?q=stoicism

# Free — list genres
curl https://book402.com/genres

# Paid — hybrid search (returns 402, needs x402 client)
curl https://book402.com/search/hybrid?q=overcoming+fear
# → 402 Payment Required (PAYMENT-REQUIRED header with payment instructions)

Pricing¶

Endpoint	Price	What you get
`/books`, `/genres`, `/stats`	Free	Metadata browsing, discovery
`/search/hybrid?q=`	$0.01	BM25 + vector semantic search
`/search/summaries?q=`	$0.01	Full-text search in summaries
`/books/:id/summary`	$0.05	Complete AI-generated book summary

Links¶

:globe_with_meridians: Live: book402.com
:bar_chart: Graph Explorer: book402.com/graph
:material-github: Source: github.com/hugofreire/book402.com
:material-book-open-variant: x402 Protocol: x402.org