book-metadata-mcp

An MCP server that searches Google Books and Open Library to find book metadata, cover art, and publication info. Built for use with Claude Code, Claude Desktop, and any MCP-compatible client.

Features

• Multi-source search — Queries Google Books and Open Library simultaneously, scores results by match quality
• One-call lookup — find_book returns title, authors, year, description, ISBNs, subjects, and cover in a single call
• High-res covers — Google Books covers up to ~1280px wide (6 sizes), Open Library L-size covers
• Smart scoring — Title/author matching with study guide detection (CliffsNotes, SparkNotes automatically deprioritized)
• Accurate publication years — Cross-references both sources, picks the earliest credible year (avoids modern reprint dates)
• Batch mode — Search up to 20 books at once
• Tool annotations — MCP behavior hints enable client auto-approval of safe read-only tools
• Instructional errors — Error responses include suggestions to help agents self-correct
• No API keys required — Works out of the box with free tiers

Tools

Tool	Description
find_book	Recommended. Complete single-book lookup — returns title, authors, year, description, ISBNs, subjects, and cover in one call.
search_book	Search by title, author, or ISBN. Returns multiple scored candidates from both sources.
get_cover	Find the best available cover image URL (prioritizes largest size). Supports dimension verification.
get_metadata	Get merged metadata: author, year, description, ISBN, subjects, page count.
download_cover	Download cover image and save as JPEG. Requires Pillow.
bulk_search	Search multiple books at once (up to 20 per batch).

Installation

Claude Code

claude mcp add book-metadata -- uvx book-metadata-mcp

Claude Desktop

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "book-metadata": {
      "command": "uvx",
      "args": ["book-metadata-mcp"]
    }
  }
}

From source

git clone https://github.com/colonylibrary/book-metadata-mcp.git
cd book-metadata-mcp
pip install -e ".[covers]"

Then register with Claude Code:

claude mcp add book-metadata -- book-metadata-mcp

Usage Examples

Once installed, the tools are available to your AI assistant:

"Search for The Great Gatsby by F. Scott Fitzgerald"

{
  "query": {"title": "The Great Gatsby", "author": "F. Scott Fitzgerald"},
  "result_count": 5,
  "results": [
    {
      "source": "open_library",
      "title": "The Great Gatsby",
      "authors": ["F. Scott Fitzgerald"],
      "published_date": "1920",
      "cover_url": "https://covers.openlibrary.org/b/id/10590366-L.jpg",
      "match_score": 95.0
    }
  ]
}

"Get the cover for Dune by Frank Herbert"

Returns URLs for the largest available cover from Google Books (up to extraLarge ~1280px) with fallback to Open Library.

"Look up metadata for these books: 1984, Brave New World, Fahrenheit 451"

Batch mode searches all three, returning title, author, year, ISBN, and cover URL for each.

Configuration

All configuration is optional via environment variables:

Variable	Default	Description
GOOGLE_BOOKS_API_KEY	(none)	Optional Google API key for higher quota (1,000/day without)
GOOGLE_DELAY	0.5	Seconds between Google API calls
OPENLIBRARY_DELAY	0.35	Seconds between Open Library API calls
GOOGLE_CB_THRESHOLD	3	Consecutive 429 failures before circuit breaker trips
GOOGLE_CB_COOLDOWN	60	Seconds to skip Google after circuit breaker trips
BOOK_MCP_USER_AGENT	BookMetadataMCP/0.2.0	User-Agent for API requests

Bulk Usage / Rate Limiting

Google Books allows ~1,000 requests/day without an API key. For libraries larger than ~500 books, you'll hit rate limits. The server handles this automatically:

1. Circuit breaker — After 3 consecutive 429 responses, Google is skipped for 60 seconds
2. Graceful fallback — Open Library continues serving results during Google cooldown
3. Auto-recovery — Google is retried after the cooldown period expires
4. Zero errors — Rate limiting never causes failures, just temporary loss of Google-specific data

For the best bulk experience, set GOOGLE_BOOKS_API_KEY to a Google Cloud API key with Books API enabled (free tier: 1,000/day; paid: higher).

How Scoring Works

Each result is scored on a 0-100+ scale:

Factor	Points	Description
Title match	0-50	Exact match = 50, partial = proportional
Author match	0-30	Exact = 30, partial/substring = 20
Has cover	10	Cover image URL available
Has description	5	Book description available
Has ISBN	5	ISBN-10 or ISBN-13 available
Google source	2	Slight preference for cover quality
Study guide	-60	CliffsNotes, SparkNotes, etc.
Inflated title	-15	Result title much longer than query

Data Sources

Google Books API

• Publisher-verified metadata
• 6 cover image sizes (smallThumbnail through extraLarge)
• Rich descriptions from publishers
• Free: 1,000 requests/day without API key

Open Library API

• Community-curated metadata
• Original publication years (first_publish_year)
• Extensive subject classification
• Free: 3 requests/sec with User-Agent header

Stress Test Results

Tested against 1,920 audiobook titles (v0.1.3, fresh install, no API key):

Metric	Result
Match rate	92.2% (1,752 / 1,901 processed)
Errors	0
High-confidence matches (>=70)	80% (1,523)
Has cover URL	85% (1,629)
Has ISBN	75% (1,444)
Has publication year	99.9% of matches
Speed	0.5-0.7 books/sec
Google 429 handling	Circuit breaker tripped, graceful OL fallback

All 5 tools pass: search_book, get_cover, get_metadata, download_cover, bulk_search. Edge case tests: 26/26 passed (Unicode, short titles, empty inputs, special characters, ISBN lookup, bulk limits).

License

MIT