Hosted EPUBCheck: check an EPUB file against the EPUB specification and list every error.
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Your API key; signing in with OAuth works instead
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Check an EPUB file (EPUB 2 or 3) against the EPUB specifications with EPUBCheck, the W3C's conformance checker. Input: `epub_base64` is the base64 of the EPUB, at most 4 MB decoded, or pass the file as a download link in `file`. Returns `summary` (`valid`, and the `fatal`, `error` and `warning` counts; `valid` is true when there is no FATAL and no ERROR message), `messages` (the 20 most severe, FATAL first, each with `severity`, `id`, `message`, up to three `locations` as `path:line:column`, and a `suggestion` when EPUBCheck has one), `messages_total` and `epubcheck_version`. For the full report, or files up to 25 MB, use the REST API (`POST /v1/epubcheck/check`). Credits: 2 per call.
The file as a download link, instead of `epub_base64`. In ChatGPT, pass the user's uploaded file here. Other clients can set `download_url` to a public https URL.
The EPUB file, base64-encoded. At most 4 MB decoded.
Pick your client. Values in capitals, like YOUR_TOKEN, are yours to fill in.
Run in a terminal
claude mcp add --transport http epubcheck https://api.pagespool.com/mcp/epubcheck/
Headers
X-API-Key (optional, not in the config above): Your API key; signing in with OAuth works insteadCheck an EPUB file (EPUB 2 or 3) against the EPUB specifications with EPUBCheck, the W3C's conformance checker. Input: `epub_base64` is the base64 of the EPUB, at most 4 MB decoded, or pass the file as a download link in `file`. Returns `summary` (`valid`, and the `fatal`, `error` and `warning` counts; `valid` is true when there is no FATAL and no ERROR message), `messages` (the 20 most severe, FATAL first, each with `severity`, `id`, `message`, up to three `locations` as `path:line:column`, and a `suggestion` when EPUBCheck has one), `messages_total` and `epubcheck_version`. For the full report, or files up to 25 MB, use the REST API (`POST /v1/epubcheck/check`). Credits: 2 per call.
| Argument | Type | Description |
|---|---|---|
| file | object | The file as a download link, instead of `epub_base64`. In ChatGPT, pass the user's uploaded file here. Other clients can set `download_url` to a public https URL. |
| epub_base64 | any | The EPUB file, base64-encoded. At most 4 MB decoded. |
{
"type": "object",
"properties": {
"file": {
"type": "object",
"default": null,
"required": [
"download_url",
"file_id"
],
"properties": {
"file_id": {
"type": "string",
"description": "An identifier for the file. ChatGPT sets it; other clients may pass any label, such as the file name."
},
"file_name": {
"type": "string"
},
"mime_type": {
"type": "string"
},
"download_url": {
"type": "string",
"description": "A public https URL of the file."
}
},
"description": "The file as a download link, instead of `epub_base64`. In ChatGPT, pass the user's uploaded file here. Other clients can set `download_url` to a public https URL."
},
"epub_base64": {
"anyOf": [
{
"type": "string"
},
{
"type": "null"
}
],
"default": null,
"description": "The EPUB file, base64-encoded. At most 4 MB decoded."
}
},
"additionalProperties": false
}We read every tool's name, description and inputs the way the model will, looking for instructions hidden from you. A clean result means no warning signs, not a guarantee. Scanned Nov 4, 2026.