calibre-mcp

# 📚 calibre-mcp [](https://www.npmjs.com/package/calibre-mcp) [](https://www.npmjs.com/package/calibre-mcp) [](https://registry.modelcontextprotocol.io) [](https://github.com/caelum29/calibre-mcp/actions/workflows/ci.yml) [](https://nodejs.org) [](./LICENSE) [](https://skills.sh/caelum29/calibre-mcp) > **The most capable Calibre MCP server in existence** — connect Claude (or any MCP client) > to your [Calibre](https://calibre-ebook.com) ebook library and search it by *meaning*, not > just keywords. Ask your AI assistant *“which of my books explain consumer-group rebalancing?”* and get the exact chapter — across 800+ books or inside one. Curate metadata, dedupe, and safely edit your library, all through natural language. <p align="center"> <img src="https://raw.githubusercontent.com/caelum29/calibre-mcp/main/demo.gif" width="720" alt="Claude Desktop searching a Calibre library and rendering the results as an interactive cover carousel" /> <br/> <em>Claude Desktop rendering a library search as an interactive cover board (MCP&nbsp;Apps)</em> </p> ## ✨ Highlights - **17 tools** covering the full surface: search, read content, browse categories, curate, and (opt-in) write — update metadata, bulk-edit, merge duplicates, import, delete. - **Semantic search** — meaning-based, hybrid vector + keyword retrieval over your whole library *or inside a single book*. Multilingual (English + Russian verified, cross-lingual queries work). No other Calibre MCP server has this. - **In-chat UI (MCP Apps)** — in hosts that support MCP Apps (Claude Desktop), library searches render an interactive cover carousel and `calibre_get_book` a book detail card with cover, rating, and read/similar actions. Text-only hosts are unaffected. - **Curation tools** — find duplicates with merge-safety scoring, audit metadata quality, and recover real metadata for books with raw filenames (`795731065.pdf` → *Fundamentals of Software Engineering*) via Open Library / Google Books. - **Safe by default** — read-only unless you explicitly enable writes; destructive operations preview first and require confirmation; all writes route through the Content Server so they never race the Calibre GUI. ## 📋 Requirements - **Calibre** with the **Content Server running** (in Calibre: *Connect/share → Start Content server*). Tested against Calibre 9.x; any recent version should work. - **Node.js ≥ 22.5** for the npm/npx install (not needed for the Claude Desktop one-click bundle — Desktop ships its own runtime). - Optional, for best PDF text extraction: poppler's `pdftotext` (`brew install poppler`) or Python 3 with PyMuPDF (`pip install pymupdf`). Without them the server falls back to Calibre's `ebook-convert`. ## 🚀 Quick start ### Easiest — let your agent install it for you Grab the guided-installer skill and hand the whole job to your agent: ```sh npx skills@latest add caelum29/calibre-mcp # pick calibre-mcp-setup ``` Then tell your agent: **"set up calibre-mcp"**. The `calibre-mcp-setup` skill drives everything below — preflight (Node, calibredb, Content Server), the Calibre-side config, the right install for your client (macOS/Windows/Linux), and a `calibre_ping` verification — asking you only the questions that are yours to answer (which client, writes on/off). Works in any Agent-Skills-compatible harness (Claude Code, Copilot, Amp, …). Prefer doing it by hand? Pick your client below. ### Claude Code MCP server only: ```sh claude mcp add calibre -- npx -y calibre-mcp ``` Or install the plugin — server **and** the companion skills in one step, with a settings dialog (server URL, library, write gate) at install time: ``` /plugin marketplace add caelum29/calibre-mcp /plugin install calibre-mcp@caelum29 ``` ### Claude Desktop (one-click) Download the `.mcpb` bundle from the [latest release](https://github.com/caelum29/calibre-mcp/releases/latest) and open it — Claude Desktop installs it and prompts for settings (server URL, library, writes on/off). No terminal needed. > **About the install warning.** Claude Desktop shows *“Installing will grant this > extension access to everything on your computer… developer information has not been > verified by Anthropic”* for **every** extension installed from a file rather than the > built-in directory — it’s not specific to this one. The server runs as a local Node > process under your user account, exactly like the `npx` install below; the bundle is > built and published by CI from this repository, so you can audit what you’re running. > Click **Install** to proceed. > The bundle ships without the optional embeddings dependency to stay small, so the two > semantic-search tools report themselves unavailable. Metadata and full-text search work > fully. For semantic search, use the npx install below instead. ### Claude Desktop (JSON config) Add to `claude_desktop_config.json`: ```json { "mcpServers": { "calibre": { "command": "npx", "args": ["-y", "calibre-mcp"] } } } ``` ### Cowork Configure the server in Claude Desktop (either method above) — Desktop bridges local MCP servers into Cowork automatically. No extra setup. ### Skills only — any agent (Claude Code, Codex, Cursor, …) The repo's Agent Skills — a guided installer (`calibre-mcp-setup`), the calibre-mcp usage guide, and the two distill skills — install into any Agent-Skills-compatible harness with the [skills.sh](https://skills.sh) installer: ```sh npx skills@latest add caelum29/calibre-mcp ``` Pick the skills and target agents interactively. Two philosophies, same as [mattpocock/skills](https://github.com/mattpocock/skills): **skills.sh copies** the files into your setup so you can hack on them; the **Claude Code plugin** (above) keeps them as a managed, auto-updating bundle. Either way the skills drive this MCP server's tools, so install the server too — or let the `calibre-mcp-setup` skill do it: it walks any agent through preflight, per-client install (macOS/Windows/Linux), and verification. ### First contact — a five-prompt tour The server auto-detects your default library; if the Content Server isn’t reachable it logs an actionable hint to stderr. Then try, in order: 1. *“list my calibre libraries”* — connectivity sanity check. 2. *“find books about Rust”* — metadata search; in Claude Desktop the results render as the cover carousel above. 3. *“show me The Rust Programming Language”* — full metadata; renders as a book card with cover, rating, and per-format read buttons. 4. *“build the semantic index for my Kafka books”* — one-time prep for meaning-based search (see below). 5. *“which of my books explain consumer-group rebalancing?”* — semantic search; answers with ranked books, or exact passages when scoped to one book. Bonus: *“what’s wrong with my library?”* runs the quality audit (missing metadata, raw-filename titles, invalid ISBNs). ## ✍️ Enabling writes Write tools (`calibre_update_book`, `calibre_bulk_update`, `calibre_add_book`, `calibre_remove_book`, `calibre_merge_books`) are **hidden by default**. Two independent switches must be on: 1. **The MCP-side gate** — set `CALIBRE_MCP_ENABLE_WRITE=1` (or tick *Enable writes* in the Desktop bundle settings). Without it the write tools aren’t even registered. 2. **The Calibre-side gate** — the Content Server must allow local writes. **By default the server embedded in the Calibre GUI is read-only**, so either enable the GUI option below or run a standalone server with `--enable-local-write`: ```sh # quit the Calibre GUI first (it holds the library lock), then: calibre-server --enable-local-write --port 8080 "/path/to/Calibre Library" ``` Or enable it on the **GUI-embedded** server without quitting the app: open Calibre → **Preferences → Sharing over the net → Advanced** and tick **“Allow un-authenticated local connections to make changes to the library”** (i.e. permit local write access), then restart the Content Server from the GUI. This is the `--enable-local-write` equivalent for the embedded server. With only the first switch on, write tools appear but Calibre refuses the write — the error message tells you exactly that. Reads work fine against the GUI-embedded server. Safety behavior: `calibre_bulk_update` requires an explicit book selection (`ids` or `query` — there is no “all books” default) and previews changes until you pass `preview: false`. `calibre_remove_book` is a dry-run until you pass `confirm: true`; deletion removes records *and* files, permanently. `calibre_merge_books` shows its full merge plan until you pass `confirm: true`, and trashed sources stay recoverable from Calibre's trash (mode `safe` keeps them entirely). `calibre_add_book` only imports files from whitelisted folders (`CALIBRE_MCP_ADD_ROOTS`). ## 🔎 Semantic search > Deep dive: [`docs/SEMANTIC-SEARCH.md`](./docs/SEMANTIC-SEARCH.md) — how indexing, hybrid retrieval, and reranking work. Meaning-based search is **opt-in** and needs two things: 1. **The embeddings dependency** — `@huggingface/transformers` is an `optionalDependencies` entry, so a normal `npx calibre-mcp` / `npm install` gets it automatically. (Only the MCPB bundle excludes it.) 2. **An index** — ask Claude to run `calibre_build_index` for the books you care about (by ids or a Calibre query). The first build downloads the embedding model (`multilingual-e5-small`, ~118 MB, one-time) into the index directory; after that everything runs offline. Indexing runs at roughly 100 chunks/sec on Apple Silicon. > [!IMPORTANT] > **Search results are sharpened by a cross-encoder reranker whose model is a separate > ~576 MB one-time download.** `calibre_build_index` pre-downloads it during the build — > the step you already expect to be slow. If you skip straight to searching on a machine > without the cached model, your **first** hybrid/vector search triggers that download > instead. Reranking also adds seconds of CPU per semantic search; set > `CALIBRE_MCP_RERANK=off` to disable it (faster, noticeably less precise ranking). Then `calibre_semantic_search` answers queries like *“which of my books explain consumer group rebalancing?”* — across the library (`scope: library`, ranks books) or within one book (`scope: book`, returns located passages). Retrieval is **hybrid** by default: vector cosine + stemmed keyword FTS, fused with reciprocal rank fusion, then reranked by the cross-encoder (top 30 candidates) when its model is available. Queries in one language find passages in another (EN⇄RU verified). **No embeddings? Keyword search still works.** `mode: keyword` uses no model *at query time*, but it needs an index. If the embedding model isn’t installed (the default MCPB bundle ships without it), build a **keyword-only** index — `calibre_build_index` with `keywordOnly: true`, or it happens automatically when the model is absent — and search with `mode: keyword`. That path has zero ML dependencies. `mode: vector` then errors actionably and `mode: hybrid` degrades to keyword (with a note); rebuild with the model installed (`force: true`) to add semantic ranking. ## 🧰 Tools > Full reference with parameters and examples: [`docs/TOOLS.md`](./docs/TOOLS.md). | Tool | Access | What it does | |---|---|---| | `calibre_search` | read | Find books by title/author/ISBN/tag or Calibre query syntax (`mode: meta`), or full text (`mode: fts`); `scope: book` searches inside one book | | `calibre_get_book` | read | Full metadata, formats, and cover link for one book (id or uuid); `include_cover: true` embeds the cover image in the result | | `calibre_get_content` | read | Read a book’s text as capped excerpts; walk the whole book via cursor. `structure: true` returns a chapter map (headings, offsets, per-chapter cursors) — EN + RU/UK | | `calibre_list_categories` | read | Browse tags, authors, series, publishers, custom columns with counts | | `calibre_list_libraries` | read | List the libraries the Content Server exposes (+ which is default) | | `calibre_semantic_search` | read | Meaning-based search; `mode: hybrid\|vector\|keyword`, library- or book-scoped | | `calibre_build_index` | read* | Build/refresh the local semantic index for selected books (writes only a local index file); `keywordOnly: true` builds a model-free keyword index | | `calibre_find_duplicates` | read | Duplicate groups with merge-safety scores; `mode: compare` diffs two books | | `calibre_quality_report` | read | Audit: missing metadata, raw-filename titles, invalid ISBNs, author-sort issues, series gaps | | `calibre_recover_metadata` | read | Propose real metadata via Open Library → Google Books; **preview-only**, apply with `calibre_update_book` | | `calibre_extract_isbn` | **write** | Scan a book’s own text for a valid ISBN and set its `isbn` identifier; preview-first, apply with `apply: true` | | `calibre_update_book` | **write** | Set metadata fields on one book (incl. `#custom` columns); returns the applied diff | | `calibre_bulk_update` | **write** | Same change across a set of books; selection required, preview-first | | `calibre_add_book` | **write** | Import a local ebook file (path-whitelisted) | | `calibre_remove_book` | **write, destructive** | Permanently delete books (records + files); dry-run unless confirmed | | `calibre_merge_books` | **write, destructive** | Merge duplicate records: move formats into a target, merge metadata per Calibre's rules, trash sources; dry-run plan unless confirmed | | `calibre_ping` | read | Health check: is Calibre reachable end-to-end? | In MCP Apps hosts, `calibre_search` and `calibre_semantic_search` (library scope) render their results as a cover-board carousel and `calibre_get_book` as a book card — covers load from your local Content Server. Everywhere else the same tools return their usual text results; no configuration needed either way. ## 📚 Companion skill: calibre-distill An Agent Skill that distills a book from your library into a reusable, structured skill (frameworks, mental models, glossary, cheatsheet) by driving the tools above — the chapter map (`calibre_get_content structure=true`) plus in-book keyword + semantic search. Works on EN and RU/UK books, no temp files, and can optionally stamp what you learned back into the catalog (tags + a distill note) through the gated write tools. It ships in this repo at [`skills/calibre-distill/`](./skills/calibre-distill). Install it via `npx skills@latest add caelum29/calibre-mcp` or the Claude Code plugin (see [Quick start](#-quick-start)), or manually by symlinking: ```sh ln -s "$PWD/skills/calibre-distill" ~/.claude/skills/calibre-distill ``` Then ask, e.g., *“distill book 187 into a skill called kafka-ops”*. Note: the MCPB bundle can’t ship skills — install the skills separately from the MCP server on Claude Desktop. ### Companion skill: calibre-distill-topic A sibling skill that synthesizes **one topic across several books** (≥3) into a single **concept-keyed** skill — a decision framework, per-concept sections, a cross-source config table, an explicit *“where the sources disagree or complement”* section, and an ISBN bibliography that doubles as a live-source binding. Use it when you want a topic study aid built from a shelf of books rather than a single-book distill (single-book requests belong to `calibre-distill`). Ships at [`skills/calibre-distill-topic/`](./skills/calibre-distill-topic); installed by the same skills.sh / plugin / symlink paths as above. Then ask, e.g., *“synthesize kafka reliability from books 187 182 571 186 into a skill.”* Generated skills can be checked with the bundled verifier — verbatim-overlap (8-gram shingles vs the source books), quote budget, compression floor, heading mirroring, cursor leaks, and attribution: ```sh pnpm build && node scripts/legal-gate.mjs <skill-dir> --book <id> [--book <id>…] ``` ## ⚙️ Configuration Everything is optional — with a running Content Server on the default port, zero config works. Environment variables (the Desktop bundle exposes the same settings as UI fields): | Variable | Default | Purpose | |---|---|---| | `CALIBRE_MCP_SERVER_URL` | `http://localhost:8080` | Calibre Content Server base URL | | `CALIBRE_MCP_LIBRARY` | *auto-detect* | Library name; empty = the server’s default library | | `CALIBRE_MCP_ENABLE_WRITE` | off | Master write gate (`1`/`true`/`yes`) | | `CALIBRE_MCP_CALIBREDB_PATH` | *auto-discover* | `calibredb` binary; found via standard install paths, then `PATH` | | `CALIBRE_MCP_INDEX_DIR` | platform data dir¹ | Semantic index + embedding-model cache | | `CALIBRE_MCP_SEMANTIC_FLOOR` | `0.78` | Cosine score below which semantic results are flagged low-confidence | | `CALIBRE_MCP_RERANK` | on | Cross-encoder rerank stage on semantic search (~576 MB model, seconds of CPU per query); set `off`/`false`/`0` to disable | | `CALIBRE_MCP_MAX_BOOK_BYTES` | `268435456` (256 MB) | Largest book download `calibre_build_index` / `calibre_get_content` will extract; bigger books are skipped² | | `CALIBRE_MCP_ADD_ROOTS` | `~/Documents`, `~/Downloads` | Folders `calibre_add_book` may import from (path-delimiter separated) | | `CALIBRE_MCP_BOARD_STYLE` | `shelf` | Search-results widget style in MCP Apps hosts: `shelf` (scrolling cover shelf) or `coverflow` (3D cover flow; the Desktop bundle exposes this as a *Coverflow search results* toggle) | ¹ macOS `~/Library/Application Support/calibre-mcp/index`, Windows `%APPDATA%\calibre-mcp\index`, Linux `$XDG_DATA_HOME/calibre-mcp/index`. ² Size the cap against what the **Content Server serves**, not the file on disk — it can hand back a much heavier copy (an 8 MB PDF served as 70 MB), so a disk-sized cap silently skips books. ## 🩺 Troubleshooting > More symptoms and fixes: [`docs/TROUBLESHOOTING.md`](./docs/TROUBLESHOOTING.md). - **“Calibre unreachable” / connection refused** — the Content Server isn’t running. In Calibre: *Connect/share → Start Content server*, or point `CALIBRE_MCP_SERVER_URL` at the right host/port. - **Write refused / “Forbidden”** — the Content Server doesn’t allow local writes. See *Enabling writes* above: run a standalone server with `--enable-local-write`, or tick the GUI’s *Sharing over the net → Advanced* option and restart the Content Server. - **Full-text search returns nothing / errors** — Calibre’s FTS index isn’t enabled for the library. In Calibre: *Preferences → Searching → Full text search*, enable it, and let indexing finish (it can take a while on large libraries). - **“embedding model unavailable”** — the optional `@huggingface/transformers` package isn’t installed (expected with the MCPB bundle). Use the npx install, or `npm install @huggingface/transformers` next to the server. To search without it, build a keyword-only index (`calibre_build_index keywordOnly=true`) and use `mode: keyword`. - **`calibredb` not found** — install Calibre, or set `CALIBRE_MCP_CALIBREDB_PATH` to the binary (macOS: `/Applications/calibre.app/Contents/MacOS/calibredb`). - **A PDF extracts to empty text** — it’s a scanned/image PDF; Calibre has no OCR, and neither do we. - **Library not found (404)** — pass the library’s *display name* or *ID* as shown by `calibre_list_libraries`; when in doubt, leave the library unset and let the server pick its default. ## 🛠️ Development ```sh pnpm install pnpm build # tsc → dist/ pnpm test # vitest (unit; no network, no model download) pnpm test:model # gated embedding-model integration tests (~118 MB download) pnpm inspect # MCP Inspector against the built server pnpm pack:mcpb # build the Claude Desktop .mcpb bundle ``` The codebase is Clean Architecture: tool handlers, Calibre clients, and the semantic core are SDK-free; only `src/server.ts` touches the MCP SDK. User docs — the tool reference and the semantic-search guide — live in [`docs/`](./docs). Questions, ideas, and setups welcome in [**Discussions**](https://github.com/caelum29/calibre-mcp/discussions); bug reports and PRs in [Issues](https://github.com/caelum29/calibre-mcp/issues). ## 📄 License [MIT](./LICENSE) © 2026 Artem Sorochynskyi An independent project, not affiliated with Calibre. [Calibre](https://calibre-ebook.com) itself is [Kovid Goyal's open-source project](https://github.com/kovidgoyal/calibre) (GPLv3) — this server drives it as a separate program via `calibredb` and the Content Server.