MCP Open Library

A Model Context Protocol (MCP) server for the Open Library API that enables AI assistants to search for book and author information.

This project implements an MCP server that provides tools for AI assistants to interact with theOpen Library. It allows searching the catalogue by title, author, subject and other fields, searching for authors by name, retrieving detailed author information using their Open Library key, and getting URLs for book covers and author photos. The server returns JSON projections of the Open Library responses rather than the raw payloads.

{ "mcpServers": { "mcp-open-library": { "command": "npx", "args": ["-y", "mcp-open-library"] } } }

In Claude Desktop that goes inclaude_desktop_config.json; other clients use the same shape. Restart the client and the seven tools below become available.

This server publishes to the official MCP Registry asio.github.8enSmith/mcp-open-libraryfrom v1.0.3 onwards. Clients that support the registry can install it by that name.

curl "https://registry.modelcontextprotocol.io/v0.1/servers?search=io.github.8enSmith/mcp-open-library"

To install MCP Open Library for Claude Desktop automatically viaSmithery:

npx -y @smithery/cli install @8enSmith/mcp-open-library --client claude

# Clone the repository git clone https://github.com/8enSmith/mcp-open-library.git cd mcp-open-library # Install dependencies npm install # Build the project npm run build

This server implements the Model Context Protocol, which means it can be used by any MCP-compatible AI assistant or client e.g.Claude Desktop. The server exposes the following tools:

{ "author": "Ursula K. Le Guin", "subject": "fantasy", "sort": "old", "limit": 2 }

{ "num_found": 51, "offset": 0, "limit": 2, "results": [ { "title": "A Wizard of Earthsea", "authors": ["Ursula K. Le Guin"], "first_publish_year": 1968, "open_library_work_key": "/works/OL59798W", "edition_count": 87, "author_keys": ["OL31353A"], "best_edition": { "edition_key": "OL5613890M" }, "cover_url": "https://covers.openlibrary.org/b/id/13617691-M.jpg", "ratings_average": 3.95, "ebook_access": "borrowable" } ] }

best_editionis one specific edition of the work — the one Open Library ranks best for your query — carrying that edition's own identifiers. Search results otherwise identify awork(open_library_work_key), which no tool accepts, so this is the route from a search hit to a concrete book.

Itsedition_keyis an OLID you can pass straight toget_book_by_idfor the full edition record, including its complete ISBN arrays:

{ "idType": "olid", "idValue": "OL5613890M" }

Theisbn_13/isbn_10fields are omitted where Open Library holds no ISBN for that edition — as in the example above, and roughly a third of results — whileedition_keyis essentially always present. Where an edition lists several ISBNs of one kind, the first is reported;get_book_by_idreturns them all.

Thesearch_bookstool accepts the following parameters:

- At least one ofq,title,author,subject,place,person,publisherorisbn— the request is rejected without one, since an unfiltered search matches the entire catalogue.qtakes a free-form Solr query such assubject:cyberpunk AND first_publish_year:[1980 TO 1990]
- language: Optional 3-letter MARC language code (e.g.eng,fre)
- sort: Optional ordering —new,old,random,key,rating,readinglog,want_to_read,currently_reading,already_readortitle. Omit for relevance
- limit: Optional, 1–50, defaults to 10
- offset: Optional, 0–1000, defaults to 0

{ "title": "The Hobbit", "limit": 1 }

{ "num_found": 224, "offset": 0, "limit": 1, "results": [ { "title": "The Hobbit", "authors": ["J.R.R. Tolkien"], "first_publish_year": 1937, "open_library_work_key": "/works/OL27482W", "edition_count": 481, "author_keys": ["OL26320A"], "best_edition": { "edition_key": "OL51709286M", "isbn_13": "9780395520215", "isbn_10": "0395520215" }, "cover_url": "https://covers.openlibrary.org/b/id/14627509-M.jpg", "ratings_average": 4.29, "ebook_access": "borrowable" } ] }

{ "name": "J. R. R. Tolkien", "limit": 2 }

Each result'skeycan be passed toget_author_infofor that author's full record.alternate_namesis abridged here.

{ "num_found": 2, "offset": 0, "limit": 2, "results": [ { "key": "OL26320A", "name": "J.R.R. Tolkien", "alternate_names": ["John Ronald Reuel Tolkien", "Tolkien"], "birth_date": "3 January 1892", "top_work": "The Hobbit", "work_count": 355 }, { "key": "OL332676A", "name": "J. R. R. Tolkien Centenary Conference (1992 Keble College, Oxford)", "top_work": "Proceedings of the J.R.R. Tolkien Centenary Conference, 1992", "work_count": 2 } ] }

{ "author_key": "OL26320A" }

{ "name": "J. R. R. Tolkien", "personal_name": "John Ronald Reuel Tolkien", "birth_date": "3 January 1892", "death_date": "2 September 1973", "bio": "John Ronald Reuel Tolkien (1892-1973) was a major scholar of the English language, specializing in Old and Middle English. He served as the Rawlinson and Bosworth Professor of Anglo-Saxon and later the Merton Professor of English Language and Literature at Oxford University.", "alternate_names": ["John Ronald Reuel Tolkien"], "photos": [6791763], "key": "/authors/OL26320A", "remote_ids": { "viaf": "95218067", "wikidata": "Q892" }, "revision": 43, "last_modified": { "type": "/type/datetime", "value": "2023-02-12T05:50:22.881" } }

{ "olid": "OL26320A" }

https://covers.openlibrary.org/a/olid/OL26320A-L.jpg

When Open Library has no photo for that author, the tool says so instead of returning a URL:

No author photo available for OLID OL99999999A.

{ "key": "ISBN", "value": "9780547928227", "size": "L" }

https://covers.openlibrary.org/b/isbn/9780547928227-L.jpg

As with author photos, a book with no cover produces a message rather than a URL:

No cover image available for OLID OL00000000M.

Theget_book_covertool accepts the following parameters:

- key: The type of identifier (one of:ISBN,OCLC,LCCN,OLID, orID)
- value: The value of the identifier
- size: Optional cover size (Sfor small,Mfor medium,Lfor large, defaults toL)

{ "idType": "isbn", "idValue": "9780547928227" }

{ "title": "The Hobbit", "authors": [ "J. R. R. Tolkien" ], "publishers": [ "Houghton Mifflin Harcourt" ], "publish_date": "October 21, 2012", "number_of_pages": 300, "isbn_13": [ "9780547928227" ], "isbn_10": [ "054792822X" ], "oclc": [ "794607877" ], "olid": [ "OL25380781M" ], "open_library_edition_key": "/books/OL25380781M", "open_library_work_key": "/works/OL45883W", "cover_url": "https://covers.openlibrary.org/b/id/8231496-M.jpg", "info_url": "https://openlibrary.org/books/OL25380781M/The_Hobbit", "preview_url": "https://archive.org/details/hobbit00tolkien" }

Theget_book_by_idtool accepts the following parameters:

- idType: The type of identifier (one of:isbn,lccn,oclc,olid)
- idValue: The value of the identifier

An example of this tool being used in Claude Desktop can be see here:

You can test this MCP server using Docker. To do this first run:

docker build -t mcp-open-library . docker run -p 8080:8080 mcp-open-library

You can then test the server running within Docker via the inspector e.g.

- src/index.ts- The MCP server: builds the HTTP clients and drives both request handlers from the tool registry
- src/index.test.ts- Tests for the server wiring, including a snapshot of the published tool schemas
- src/tools/<tool-name>/- One directory per tool, each containingindex.ts(the handler, its Zod argument schema and itsToolDefinition),index.test.ts, and — for tools with a non-trivial API response — atypes.tsdescribing that response shape
- src/tools/registry.ts- TheTOOLSarray, the single list of what the server exposes
- src/tools/types.ts- TheToolDefinitionandToolHandlercontracts
- src/utils/- Shared plumbing:http.ts(the API and covers Axios clients),errors.ts(argument parsing and error results),results.ts,schema.ts(Zod → JSON Schema),search.ts(the shared search projection and paging schemas),covers.ts
- scripts/- Release automation (sync-server-json.mjs,promote-changelog.mjs,assert-release-consistency.mjs) and its tests

A tool's input contract is declared once, as a Zod schema. The JSON Schema that MCP clients see is generated from it bytoInputSchema, so the two cannot drift. Field descriptions come from.describe()on the Zod schema. Note that.refine()constraints are dropped in translation — a cross-field rule has to be stated in the tool'sdescriptiontoo, or clients will never learn about it.

Adding a tool means creating the directory and adding one entry toTOOLSinsrc/tools/registry.ts.src/index.test.tsderives its expectations from that array, so the only test change is an updated schema snapshot (npx vitest run -u).

- npm run build- Build the TypeScript code
- npm run watch- Watch for changes and rebuild
- npm test- Run the test suite in watch mode
- npm run test:precommit- Run the test suite once and exit
- npm run lint/npm run lint:fix- Lintsrcandscriptswith ESLint
- npm run format- Format code with Prettier
- npm run inspector- Run the MCP Inspector against the server

For a single pass — what the pre-commit hook and CI run — use:

npx vitest run src/tools/get-book-by-id/index.test.ts npx vitest run -t "should return book details when given a valid OLID"

Releases are automated. Pushing avtag triggerspublish-mcp.yml, which runs the checks, publishes the package to npm, registers the new version with the MCP Registry, and then creates a GitHub Release using that version'sCHANGELOG.mdsection as the notes. Both npm and the registry authenticate over GitHub OIDC, so there are no publishing secrets to manage.

npm version patch # or minor / major git push --follow-tags

Once it prints the new tag, the commit and tag exist and the release is done locally — the next step isgit push --follow-tags,notrunningnpm versionagain. A second run attempts thenextversion, and will fail on the missing## [Unreleased]heading (which the first run consumed). That failure is safe by design, but it leavespackage.json,package-lock.jsonandserver.jsonbumped and uncommitted. Undo with:

git restore --source=HEAD --staged --worktree package.json package-lock.json server.json

# fix the problem on main and commit it first VERSION="$(node -p "require('./package.json').version")" git push origin ":v${VERSION}" # delete the remote tag e.g. git push origin :v1.0.3 git tag -d "v${VERSION}" # delete it locally git tag -a "v${VERSION}" -m "${VERSION}" # re-tag at the fixed commit git push origin "v${VERSION}"

The fix commit must leavepackage.jsonon that same version, or the consistency check will reject the tag. If npmdid*already publish, do not reuse the version — that release is immutable. Bump to the next patch instead; the guarded npm step means a re-run skips what already succeeded.

Contributions are welcome! Please feel free to submit a pull request.

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