leanpub-mcp

An MCP server for the Leanpub author API — preview, publish, royalties, coupons, readers.

Why this exists

Leanpub documents an official hosted MCP server at https://leanpub.com/api/mcp. As of 2026-09-14 that endpoint 404s on every method (GET/POST/HEAD/OPTIONS), despite the docs describing it as live ("very early beta"). This is a local stdio server that talks to the same documented REST API directly, so preview/publish workflows aren't blocked on Leanpub finishing their rollout. Drop it once leanpub.com/api/mcp actually answers.

Related MCP server: moltline-mcp

Setup

npm install

API key

Requires a Pro plan API key from https://leanpub.com/account/api_key. Resolved fresh on every tool call (never cached), checked in this order:

1. LEANPUB_API_KEY env var (literal key)

2. LEANPUB_API_KEY_FILE env var (path to a file containing the key)

3. .leanpub-api-key in the current working directory

4. ~/.config/leanpub/api_key

Writing the key to a file takes effect on the very next tool call — no server restart needed.

Register with Claude Code

As a personal, cross-project tool (recommended — keeps the machine-specific path out of any repo's committed .mcp.json):

claude mcp add --scope user --transport stdio leanpub -- node /absolute/path/to/leanpub-mcp/bin/leanpub-mcp.js

Or add to a specific project's .mcp.json:

{
  "mcpServers": {
    "leanpub": {
      "command": "node",
      "args": ["/absolute/path/to/leanpub-mcp/bin/leanpub-mcp.js"]
    }
  }
}

### MCP client timeout for `wait_for_job`

`wait_for_job` polls internally for up to `timeoutSeconds` (default 120),
but that's a single MCP tool call the whole time -- most MCP clients kill a
tool call after their own default request timeout (often 30s) regardless of
what the server is doing internally, since this server sends no progress
notifications. Confirmed live: a 180s `wait_for_job` call was killed at 30s
with `Request timeout after 30000ms` even though the underlying Leanpub job
finished fine.

Fix: set a per-server timeout in your MCP client config, comfortably above
whatever `timeoutSeconds` you pass. In Claude Code / OMP's `.mcp.json`:

```json
{
  "mcpServers": {
    "leanpub": {
      "command": "node",
      "args": ["/absolute/path/to/leanpub-mcp/bin/leanpub-mcp.js"],
      "timeout": 300000
    }
  }
}

Without that, just poll get_job_status directly in a loop (5s between calls, per Leanpub's own rate-limit guidance) instead of calling wait_for_job.

Tools

Not implemented: file upload to upload-mode books, XML response formats (JSON only). Add them if you need them — src/client.js follows one pattern per resource.

Typical workflow

Preview the book, then tell me when it's ready.

Calls preview_book, then wait_for_job, then reports the pdf_preview_url / epub_preview_url from a follow-up get_book call.

Testing

npm test          # unit tests for URL building, error parsing, key resolution

Unit tests don't hit the network. To confirm the server is wired to the real API, run verify_api_key with a real (or intentionally wrong) key and check you get back a 200 with your username, or a clean 401.