How book-to-skill Handles MOBI, AZW, and AZW3 E-Book Files

book-to-skill processes MOBI, AZW, and AZW3 files exclusively through Calibre's ebook-convert CLI tool, treating them as binary formats that require external conversion rather than native Python parsing.

The open-source project virgiliojr94/book-to-skill provides a specialized extraction pipeline for e-book formats lacking robust pure-Python parsers. For Amazon's proprietary formats—MOBI, AZW, and AZW3—the system delegates conversion entirely to Calibre's command-line utilities, implementing strict dependency validation before processing.

Configuration of Calibre-Only Extensions

In book_to_skill/config.py, the tool explicitly registers MOBI, AZW, and AZW3 as Calibre-dependent formats through the CALIBRE_EBOOK_EXTENSIONS tuple. This configuration at lines 37-40 serves as the canonical registry that routes these file types through the external conversion pipeline, distinguishing them from formats handled by native Python libraries.

# From book_to_skill/config.py (simplified conceptual view)

CALIBRE_EBOOK_EXTENSIONS = ('.mobi', '.azw', '.azw3')

Hard Dependency on Calibre CLI

Unlike EPUB or PDF handling, which may utilize Python packages such as ebooklib or PyPDF2, MOBI/AZW/AZW3 processing requires the external ebook-convert binary. The book_to_skill/dependencies.py module declares this as a mandatory system dependency at lines 61-68, ensuring the extraction pipeline acknowledges that no fallback parser exists for these formats.

Pre-Flight Validation and Error Handling

Before any content extraction occurs, the prepare_dependencies() function in book_to_skill/utils.py performs extension-based validation. When encountering a file extension contained within CALIBRE_EBOOK_EXTENSIONS, the code verifies that ebook-convert exists on the system PATH (lines 30-34).

If the binary is absent, the system immediately raises an ExtractionError with explicit installation instructions rather than attempting parsing and failing with cryptic errors. This early validation ensures users receive actionable feedback before the extraction process begins.

The Calibre Extraction Pipeline

For validated files, the main extraction orchestration in book_to_skill/utils.py routes execution through a dedicated Calibre branch. Upon detecting a matching extension (lines 50-58), the code invokes extract_with_ebook_convert() from book_to_skill/parsers/calibre.py.

This function (lines 10-24) performs the following operations:

1. Generates a temporary output path within the configured OUTPUT_DIR
2. Executes ebook-convert [input] [output.txt] as a subprocess
3. Reads the resulting plain-text file into memory
4. Returns the content for further processing

The extracted text subsequently flows through the standard sanitization, token estimation, and metadata collection pipelines, processing identically to PDF or EPUB content once converted.

Running book-to-skill with Amazon Formats

Use the CLI entry point at scripts/extract.py to process MOBI, AZW, or AZW3 files:

# Basic extraction of a MOBI file

python3 scripts/extract.py path/to/book.mobi

# Disable interactive installation prompts for CI environments

python3 scripts/extract.py path/to/book.azw3 --install-missing no

For programmatic access within Python applications:

from book_to_skill import extract

metadata = extract("path/to/book.azw")
print(metadata["text"][:200])          # First 200 characters of extracted text

print(metadata["extraction_method"])   # Output: "ebook-convert"

Both approaches require Calibre installed locally with ebook-convert available on the system PATH.

Summary

• MOBI, AZW, and AZW3 are registered in CALIBRE_EBOOK_EXTENSIONS inside book_to_skill/config.py
• The system mandates Calibre's ebook-convert binary as declared in book_to_skill/dependencies.py
• Pre-flight checks in prepare_dependencies() verify tool availability before processing
• Extraction occurs via extract_with_ebook_convert() in book_to_skill/parsers/calibre.py
• Converted text enters the standard sanitization pipeline identical to other formats

Frequently Asked Questions

Does book-to-skill require Calibre for MOBI files?

Yes. According to the source code in book_to_skill/dependencies.py, MOBI, AZW, and AZW3 formats have a hard requirement for the ebook-convert command provided by Calibre. No pure-Python fallback parser exists for these formats within the codebase.

What happens if ebook-convert is not installed?

The prepare_dependencies() function in book_to_skill/utils.py detects the missing binary during pre-flight validation and raises an ExtractionError with clear installation instructions. The extraction aborts before any file processing begins, preventing partial or corrupted outputs.

Can I convert AZW3 files without installing the full Calibre suite?

No. The extract_with_ebook_convert() function in book_to_skill/parsers/calibre.py explicitly invokes the Calibre CLI tool. The repository contains no alternative parsing logic for these proprietary Amazon formats, making Calibre a non-negotiable system dependency for AZW3 support.

How does the error handling differ between Calibre and native formats?

For native formats like EPUB, missing dependencies may trigger interactive installation prompts or alternative parser attempts. For MOBI/AZW/AZW3, the code path in book_to_skill/utils.py (lines 30-34) treats missing ebook-convert as a fatal configuration error, immediately terminating with an explanatory exception rather than attempting recovery.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}