apibase

Search Project Gutenberg

books.gutendex.search

Read-onlyIdempotent

Search 78K+ public-domain books on Project Gutenberg by free-text query, language (ISO 639-1), topic, or author birth year. Returns book IDs, titles, authors, languages, subjects, download counts, and EPUB/TXT/HTML/cover URLs (Gutendex MIT)

Input Schema

TableJSON Schema

Name	Required	Description
`limit`	No	Max results to return (default 20, max 50).
`query`	No	Free-text search across title, author name, and subject (e.g. "shakespeare", "moby dick").
`topic`	No	Subject/bookshelf topic filter (e.g. "Adventure", "Children's literature").
`language`	No	ISO 639-1 language code or comma-separated codes to filter by language (e.g. "en", "fr,de").
`author_year_end`	No	Filter by author birth year — only include books from authors alive up to this year.
`author_year_start`	No	Filter by author birth year — only include books from authors alive in this period start.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`error`	No	Present only when the call failed. Includes error code, message, request_id, and any provider-specific extras.
`result`	No	Tool response payload. Shape varies per tool — consult the tool description and inputSchema. May be an object, array, string, or number depending on the upstream provider response.

Schema Changelog

Changes observed during successful MCP inspections.

First observedSep 22, 2026

TDQS

A4.1/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations (readOnlyHint=true, destructiveHint=false, idempotentHint=true, openWorldHint=true) indicate safe, idempotent read behavior. The description transparently adds that it returns a comprehensive set of fields and notes the source as Gutendex MIT. No contradiction.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Single sentence conveys purpose, scope, filters, and return data efficiently. Every element earns its place; no redundancy.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the presence of an output schema, the description suitably explains inputs and broad output domains. It covers search use cases completely and aligns with the tool's role among many sibling tools.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% with clear parameter descriptions. The description does not significantly extend parameter semantics beyond the schema but groups the filters and adds context about free-text search. Baseline 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool searches 78K+ books using multiple filters (free-text, language, topic, author birth year) and lists specific return fields. It effectively distinguishes itself from sibling tools like books.gutendex.book and books.gutendex.popular by emphasizing search capabilities.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage for searching public-domain books but does not explicitly mention when to use this tool over alternatives like books.gutendex.by_author or books.gutendex.popular. No exclusions or guidance on selecting among siblings.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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