John's Essentials

convert_ebook

eBook Converter — Convert ebooks between formats with calibre: mobi, azw3, fb2, lit and pdf → EPUB, plus epub → mobi/azw3 for older devices. EPUB is the format modern Kindles accept for send-to-device, so →epub is the recommended direction. DRM-protected books cannot be converted. pdf→epub reflows fixed pages, so quality varies with layout complexity; epub→pdf is handled by convert_document (LibreOffice). [category: convert]

Input Schema

TableJSON Schema

Name	Required	Description	Default
`to`	Yes	The format you want back. EPUB is what a modern Kindle accepts when you send a book to it, so it is the usual answer. Pick MOBI or AZW3 only for an older device.	epub
`file`	Yes	The ebook itself. Bytes are sniffed and must match 'from' (mismatch = 400). DRM-protected books always fail.
`from`	Yes	Source ebook format — REQUIRED.

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedSep 11, 2026

addedInput schema / properties / to / default
```
Added value: +"epub"
```

changedInput schema / properties / to / description

Previous value: -"Target format. EPUB is the recommended direction."New value: +"The format you want back. EPUB is what a modern Kindle accepts when you send a book to it, so it is the usual answer. Pick MOBI or AZW3 only for an older device."

changedInput schema / properties / to / enum

Previous value: -[
-  "epub",
-  "pdf",
-  "mobi",
-  "azw3"
-]New value: +[
+  "epub",
+  "mobi",
+  "azw3",
+  "pdf"
+]

First observedSep 5, 2026

TDQS

A4.4/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare the safety profile (non-readOnly, non-destructive, closed-world), so the description's added value is the operational caveats: DRM-protected books always fail, byte sniffing must match 'from' or the call 400s, and pdf→epub reflow quality varies with layout. These are real behavioral traits beyond the annotations, though return format/pagination are not addressed (not applicable without an output schema).

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

A single dense, front-loaded paragraph that leads with the action and conversion directions before caveats. Efficient overall, though the bracketed category tag and some format-list redundancy slightly dilute it.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With 3/3 required params, 100% schema coverage, and no output schema to explain, the description covers everything an agent needs: supported directions, the recommended target, failure modes (DRM, sniff mismatch), and the sibling route for the uncovered direction.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the parameters are already fully documented; the description largely restates the schema's own guidance (EPUB recommended, older-device fallback). It adds only marginal new meaning, so the baseline of 3 is appropriate.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (Convert) and resource (ebooks) and enumerates supported directions (mobi/azw3/fb2/lit/pdf → EPUB, epub → mobi/azw3). It also explicitly distinguishes itself from convert_document, which handles epub→pdf, so an agent can route correctly without opening both schemas.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives clear when-to-use guidance (→epub is the recommended direction because modern Kindles accept it), when to pick alternatives (mobi/azw3 only for older devices), and an explicit hand-off to a sibling for the one direction this tool does not cover. Also states an exclusion (DRM-protected books cannot be converted).

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All John's Essentials tools Inspect

Try in Browser

One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

Glama MCP Gateway

Add one secure layer between your agents and this server.

Resources

Need Help?