@cyanheads/openlibrary-mcp-server
Search books and authors, fetch editions, browse subjects, and resolve cover images from Open Library via MCP. STDIO or Streamable HTTP.
10 Tools • 2 Catalog Resources • 1 Agent Skill
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**Public Hosted Server:** [https://openlibrary.caseyjhand.com/mcp](https://openlibrary.caseyjhand.com/mcp)
---
## Overview
Open Library's catalog of 20M+ books, editions, authors, and subjects, plus full-text search inside Internet Archive's scanned books. Search and browse, drill from a work into its editions or an author into their works, and construct cover image URLs.
### Tools
| Tool | Description |
|:---|:---|
| `openlibrary_search_books` | Catalog search with field filters (title, author, subject, publisher, ISBN, language), a provider-selected edition, pagination, and optional live reading availability |
| `openlibrary_get_work` | Fetch a work by Open Library Work ID (OL…W) — title, description, subjects, cover IDs, and author IDs |
| `openlibrary_get_editions` | List editions of a work — publishers, languages, formats, ISBNs, and print run details |
| `openlibrary_get_edition` | Resolve up to 50 distinct identifiers per call by ISBN-10, ISBN-13, OCLC, LCCN, or Open Library Edition ID (OL…M), reporting misses and unprocessed identifiers |
| `openlibrary_search_authors` | Search authors by name — returns Author IDs, birth/death dates, top works, and subject associations |
| `openlibrary_get_author` | Fetch author detail by Open Library Author ID (OL…A) — bio, dates, photo IDs, and linked identifiers from Wikidata, VIAF, ISNI, Goodreads, and LibraryThing |
| `openlibrary_get_author_works` | List works by an author — titles, cover IDs, and Work OLIDs for drilling into editions or details |
| `openlibrary_get_subject` | Browse works by subject tag — returns matching works with edition counts and cover IDs plus the total work count |
| `openlibrary_search_inside` | Full-text search inside the scanned text of Internet Archive books — returns matching items with snippets |
| `openlibrary_get_cover_url` | Resolve a cover image URL for a book or author photo in S/M/L size — returns a direct HTTPS URL embeddable in markdown |
### Resources
| Resource | Description |
|:---|:---|
| `openlibrary://works/{work_id}` | Work detail by Open Library Work ID — title, description, subjects, cover IDs, and author IDs as injectable context |
| `openlibrary://authors/{author_id}` | Author detail by Open Library Author ID — name, bio, dates, photo IDs, and linked external identifiers as injectable context |
Both resources mirror data also available via `openlibrary_get_work` and `openlibrary_get_author` — useful for clients that don't surface MCP resources.
### Agent skill
[`openlibrary-guide`](./skills/openlibrary-guide/SKILL.md) covers edition selection, bibliography resolution, passage identification, and incomplete metadata. It is included in npm, Docker, and desktop bundles and served through MCP skill discovery and `skill://` resources.
## Capability reference
Paginated tools return at most 100 rows per call. Larger positive integer limits are clamped with a notice showing the applied limit and next offset. `OPENLIBRARY_CLAMP_LIMITS=false` restores schema rejection above 100. Text and structured output carry the same complete domain data, including arrays and numeric precision.
### `openlibrary_search_books` tool
- Free-text query with Solr field prefixes (`title:`, `author:`, `subject:`, `publisher:`, `isbn:`, `language:`) or dedicated filter parameters; 1–100 results per page (default 10), offset pagination
- `sort`: `relevance` (default), `new`, `old`, `rating`, `editions`
- `language` accepts a 3-letter MARC code or a translatable 2-letter ISO code; an untranslatable 2-letter code fails as `unknown_language_code` rather than being silently dropped
- `include_availability` adds live Internet Archive borrow/read status (~200ms latency), off by default; flags Open Library leaves out are omitted rather than reported as `false`, and `availability: null` means none was returned for the work
- Returns work-level records with edition counts, cover IDs, subjects, and Internet Archive identifiers
- Optional `matching_edition` and `matching_edition_count` preserve the Search API's selected edition and matching count. The selected edition is provider-ranked; it does not prove that every unfielded search term matches that edition
- `invalid_search_query` reports upstream HTTP 422 validation with recovery guidance; empty queries with specific filters remain supported
---
### `openlibrary_get_work` tool
- Fetch by Open Library Work ID (OL…W), optionally `/works/`-prefixed; anything else — an ISBN, an edition or author OLID — fails input validation before any request, naming `openlibrary_get_edition` (`id_type: "isbn"`) as the route from an ISBN to its work
- Returns title, description, subjects (plus place/time/people breakdowns), cover IDs, and author IDs — no author names (use `openlibrary_get_author` or `openlibrary_search_books`)
- A merged work ID stays reachable — the redirect chain is followed to the canonical record, `work_id` reports the canonical ID, and an enrichment notice names both IDs when they differ
- `not_found` when the Work ID doesn't exist or its redirect chain reaches no work
---
### `openlibrary_get_editions` tool
- List editions of a work by Work ID (OL…W), optionally `/works/`-prefixed; 1–100 per page (default 10), offset pagination, with the requested `offset` echoed in the output
- Same `work_id` validation as `openlibrary_get_work` — an ISBN resolves to its work through `openlibrary_get_edition` (`id_type: "isbn"`)
- Returns ISBN-10/13, publishers, languages, page count, cover IDs, and edition OLIDs (OL…M), plus `physical_format` and `edition_name` when recorded
- A merged work ID stays reachable — the editions of the canonical work come back under its ID in `work_id`, with an enrichment notice naming both IDs; a live work still costs one request
- `not_found` when the Work ID doesn't exist or its redirect chain reaches no work
---
### `openlibrary_get_edition` tool
- Accepts 1–1,000 input strings, deduplicates exact strings, and processes the first 50 distinct identifiers in one upstream batch; the remainder is returned as `unprocessed` for resubmission. Every identifier shares one `id_type`: `isbn` (10 or 13 digits, an ISBN-10 may end in an `X` check digit), `oclc` (numeric), `lccn` (unchecked), or `olid` (OL…M). With `OPENLIBRARY_CLAMP_LIMITS=false`, the input array is limited to 50 entries
- Partial success: identifiers that resolve return in `editions` (request order); the rest land in `unresolved` with `invalid_identifier` (malformed, never sent upstream) or `not_found` (well-formed, no record) — the call fails only when nothing resolves
- `upstream_unavailable` (retryable) when Open Library's batch lookup itself fails — an HTTP error status other than a rate limit, or an HTML page — so an upstream outage never reads as a missing edition
- Authors come inline — the edition's own credits, or ones marked `source: "work"` recovered from the parent work when the edition itself lists none; if those lookups fail, the batch still returns, and an enrichment notice names the editions whose authors are missing or shown by ID
- Returns ISBN-10/13, OCLC, LCCN, LC call numbers, publishers, all cataloged `languages`, page count, cover IDs, parent work ID, and an Internet Archive `ebook_url` when one exists. The singular `language` remains the first cataloged language; `physical_format` and `edition_name` preserve the catalog's wording when present
- If no processed identifier resolves, the existing typed error also carries every `unprocessed` identifier in its data and recovery hint
---
### `openlibrary_search_authors` tool
- Search by name — partial and alternate names match; 1–100 per page (default 10), offset pagination
- Returns Author ID (OL…A), alternate names, birth/death dates, top work, work count, top subjects, and average rating
---
### `openlibrary_get_author` tool
- Fetch by Author ID (OL…A); a leading `/authors/` prefix is stripped
- Returns bio, birth/death dates, photo IDs, and linked identifiers (Wikidata, VIAF, ISNI, Goodreads, LibraryThing)
- A merged author ID stays reachable — the response is the canonical record, and an enrichment notice names the canonical ID when it differs from the one requested
- `not_found` when the Author ID doesn't exist, names a record that is not an author (a work or edition OLID), or its redirect chain reaches no author
---
### `openlibrary_get_author_works` tool
- List works by Author ID (OL…A); 1–100 per page (default 20), offset pagination, with the requested `offset` echoed in the output
- Returns title, first-publish date, cover IDs, and Work ID (OL…W) per work
- A merged author ID stays reachable — an enrichment notice names the canonical ID when it differs from the one requested
- `not_found` when the Author ID doesn't exist, names a record that is not an author (a work or edition OLID), or its redirect chain reaches no author
---
### `openlibrary_get_subject` tool
- Subject name is trimmed, lowercased, and normalized from whitespace to underscores; 1–100 per page (default 12), offset pagination, with the requested `offset` echoed in the output
- Blank input fails as `invalid_subject` before any request
- Returns canonical subject name, normalized subject key, total work count, and per-work author names, edition count, and cover ID
- Empty results carry a recovery notice suggesting a different word form, synonym, or broader term — subject tags are user-contributed and inconsistent
---
### `openlibrary_search_inside` tool
- Full-text search across Internet Archive's scanned book text — the only tool that answers "which book contains this passage?"; quote a phrase for an exact match, unquoted terms match independently
- Usually takes 10–30 s against the live index, far above the metadata tools — reach for it deliberately, not as a general book search
- 1–100 results per page (default 10), offset pagination; each result carries a relevance score comparable only within its own result set
- Results key on Internet Archive `ia_identifier`, not Open Library work IDs — match it against `ia_identifiers` from `openlibrary_search_books` to reach the catalogue record
- `upstream_unavailable` (retryable) when the index answers without a result set, so a failed search never reads as "no book contains this"
---
### `openlibrary_get_cover_url` tool
- Resolves a cover or author-photo URL from `id` (numeric), `isbn` (10 or 13 digits, an ISBN-10 may end in an `X` check digit), or `olid` (OL…M for `target: "book"`, OL…A for `target: "author"`); `size` is `S`/`M`/`L` (default `M`)
- Identifiers are validated locally before any request — path separators, `..`, and control characters fail as `invalid_identifier`, and an author lookup by `isbn` fails as `invalid_target`
- The tool constructs the URL without fetching it; a returned URL does not verify that a cover exists
- Output URL is ready to embed directly as ``
---
### `openlibrary://works/{work_id}` resource
- Same fields as `openlibrary_get_work`, as injectable `application/json` context for a conversation about a specific book
- `work_id` comes from `openlibrary_search_books` or `openlibrary_get_author_works`; a merged ID resolves to the canonical work, whose ID the returned `work_id` carries, and an ID that is not a work (an edition or author OLID) is not found
---
### `openlibrary://authors/{author_id}` resource
- Same fields as `openlibrary_get_author`, as injectable `application/json` context for a conversation about a specific author
- `author_id` comes from `openlibrary_search_authors`; a merged ID resolves to the canonical author, whose ID the returned `author_id` carries, and an ID that is not an author (a work or edition OLID) is not found
## Features
Built on [`@cyanheads/mcp-ts-core`](https://github.com/cyanheads/mcp-ts-core): stdio and Streamable HTTP transports, pluggable auth (`none` / `jwt` / `oauth`), swappable storage (`in-memory`, `filesystem`, `Supabase`, `Cloudflare KV/R2/D1`), structured logging with optional OpenTelemetry tracing.
Open Library-specific:
- Open Library Search, Search Inside (full-text), Books, Authors, and Subjects APIs, cover URL construction, and Internet Archive availability lookups
- Work → editions and author → works drill-down, with explicit OLID cross-links between tool outputs
- Configurable `User-Agent` header (`OPENLIBRARY_USER_AGENT`) identifying the server per Open Library's bot-blocking convention
- Batch edition resolution — up to 50 ISBN/OCLC/LCCN/OLID identifiers in one upstream call, with per-identifier partial-failure reporting
- Timeouts sized per endpoint class (10 s record lookups, 30 s searches, 45 s full-text) inside a 50 s retry budget, so a slow upstream is waited on and a failing one returns a classified error before a typical 60 s client timeout; gateway errors are not retried in a loop
Agent-friendly output:
- Recovery guidance on every empty result — echoes the search criteria and suggests how to broaden a query or which offset to retry
- Merged-record disclosure — `openlibrary_get_author`, `openlibrary_get_author_works`, `openlibrary_get_work`, and `openlibrary_get_editions` follow merge redirects and surface the canonical ID via an enrichment notice when a requested ID was merged
- Per-item partial failure — `openlibrary_get_edition` returns resolved editions alongside typed `unresolved` reasons instead of failing the whole batch
- Complete text and structured output, with clamp and recovery notices preserved on both surfaces
## Getting started
Add the hosted server to Claude Code — no API key required:
```sh
claude mcp add --transport http openlibrary-mcp-server https://openlibrary.caseyjhand.com/mcp
```
Or run it locally:
```sh
claude mcp add openlibrary-mcp-server -- npx -y @cyanheads/openlibrary-mcp-server
```
For other clients, add this to the MCP config file:
```json
{
"mcpServers": {
"openlibrary-mcp-server": {
"command": "npx",
"args": ["-y", "@cyanheads/openlibrary-mcp-server"]
}
}
}
```
For Docker or a source build, see [Running the server](#running-the-server).
## Configuration
| Variable | Description | Default |
|:---|:---|:---|
| `MCP_TRANSPORT_TYPE` | Transport: `stdio` or `http` | `stdio` |
| `MCP_HTTP_PORT` | HTTP server port | `3010` |
| `MCP_HTTP_ENDPOINT_PATH` | HTTP endpoint path where the MCP server is mounted | `/mcp` |
| `MCP_SESSION_MODE` | HTTP session posture: `stateless`, `stateful`, or `auto`. Overrides the `stateless` declared in `src/index.ts`. | `stateless` |
| `MCP_PUBLIC_URL` | Public origin override for TLS-terminating reverse-proxy deployments | none |
| `MCP_AUTH_MODE` | Authentication: `none`, `jwt`, or `oauth` | `none` |
| `MCP_LOG_LEVEL` | Log level (`debug`, `info`, `warning`, `error`, etc.) | `info` |
| `MCP_GC_PRESSURE_INTERVAL_MS` | Opt-in Bun-only forced-GC pressure loop (ms). Recommended starting point if heap growth is observed: `60000`. | `0` (disabled) |
| `LOGS_DIR` | Directory for log files (Node.js only) | `/logs` |
| `STORAGE_PROVIDER_TYPE` | Storage backend: `in-memory`, `filesystem`, `supabase`, `cloudflare-kv/r2/d1` | `in-memory` |
| `OPENLIBRARY_USER_AGENT` | User-Agent sent with all Open Library API requests. Include a contact email per community convention. | `openlibrary-mcp-server casey@caseyjhand.com` |
| `OPENLIBRARY_CLAMP_LIMITS` | Clamp page limits to 100 and process the first 50 distinct edition identifiers, returning the remainder. `false` restores strict input bounds of 100 rows and 50 raw identifiers. | `true` |
| `OTEL_ENABLED` | Enable OpenTelemetry | `false` |
See [`.env.example`](./.env.example) for the full list of optional overrides.
## Running the server
### Local development
Requires [Bun v1.4.0](https://bun.sh/) or higher (or Node.js ≥ 24.0.0).
- **Clone and install:**
```sh
git clone https://github.com/cyanheads/openlibrary-mcp-server.git
cd openlibrary-mcp-server && bun install
cp .env.example .env # optional overrides; no required variables
```
- **Build and run the production version:**
```sh
# One-time build
bun run rebuild
# Run the built server
bun run start:http
# or
bun run start:stdio
```
- **Run checks and tests:**
```sh
bun run devcheck # Lint, format, typecheck, security
bun run test # Vitest test suite
bun run lint:mcp # Validate MCP definitions against spec
```
### Docker
```sh
docker run --rm -p 3010:3010 ghcr.io/cyanheads/openlibrary-mcp-server:latest
```
The image defaults to HTTP transport, stateless session mode, and logs to `/var/log/openlibrary-mcp-server`. To run it over stdio from an MCP client, use `"command": "docker"` with `"args": ["run", "-i", "--rm", "-e", "MCP_TRANSPORT_TYPE=stdio", "ghcr.io/cyanheads/openlibrary-mcp-server:latest"]`. To build locally, run `docker build -t openlibrary-mcp-server .`; OpenTelemetry peer dependencies are installed by default — build with `--build-arg OTEL_ENABLED=false` to omit them.
## Project structure
| Directory | Purpose |
|:---|:---|
| `src/index.ts` | `createApp()` entry point — registers tools and resources. |
| `src/config` | Server-specific environment variable parsing and validation with Zod. |
| `src/mcp-server/tools` | Tool definitions (`*.tool.ts`) — ten tools across Search, Books, Authors, Subjects, and Covers. |
| `src/mcp-server/resources` | Resource definitions (`*.resource.ts`) — Work and Author. |
| `src/services/open-library` | Open Library service layer — API client and domain types. |
| `skills/` | Published agent guidance, also served through MCP skill discovery. |
| `tests/` | Unit and integration tests mirroring the `src/` structure. |
## Development guide
See [`CLAUDE.md`](./CLAUDE.md) for development guidelines and architectural rules. The short version:
- Handlers throw, framework catches — no `try/catch` in tool logic
- Use `ctx.log` for logging, `ctx.state` for storage
- Register new tools and resources in the `createApp()` arrays
- Wrap external API calls: validate raw → normalize to domain type → return output schema; never fabricate missing fields
## Contributing
Issues are welcome. Run checks and tests before submitting:
```sh
bun run devcheck
bun run test
```
## License
This project is licensed under the Apache 2.0 License. See the [LICENSE](./LICENSE) file for details.