document-conversion

What this skill does

# Document Conversion

Convert documents and URLs to markdown using a three-tier
fallback strategy. This skill is infrastructure: consumer
skills reference it via dependency rather than reimplementing
conversion logic.

## When To Use

- Converting PDF, DOCX, PPTX, XLSX, HTML, or images to
  markdown for downstream processing
- Any skill that ingests external documents
- File format is not plain text or markdown

## When NOT To Use

- Content is already markdown or plain text
- You only need to read a small text file (use Read directly)

## Format Detection

Identify the document type from the URI before converting.

| Extension | Format | Tier 1 | Tier 2 |
|-----------|--------|--------|--------|
| `.pdf` | PDF | Yes | Read tool (pages) |
| `.docx`, `.doc` | Word | Yes | None |
| `.pptx`, `.ppt` | PowerPoint | Yes | None |
| `.xlsx`, `.xls` | Excel | Yes | None |
| `.html`, `.htm` | HTML | Yes | WebFetch |
| `.csv` | CSV | Yes | Read tool |
| `.json` | JSON | Yes | Read tool |
| `.xml` | XML | Yes | Read tool |
| `.png`, `.jpg`, `.jpeg`, `.gif`, `.webp` | Image | Yes | Read tool (visual) |
| `.mp3`, `.wav`, `.m4a` | Audio | Yes | None |
| `.zip` | Archive | Yes | None |
| `.epub` | E-book | Yes | None |

See `modules/format-matrix.md` for quality comparison
across tiers.

## Conversion Protocol

To convert a document to markdown:

```
1. DETECT  -- Identify format from URI extension or context
2. TRY     -- Tier 1: MCP markitdown (best quality)
3. DEGRADE -- Tier 2: native Claude Code tools (if Tier 1 fails)
4. INFORM  -- Tier 3: tell user what's needed (if no coverage)
5. SANITIZE -- Apply content-sanitization (external content)
```

### Tier 1: MCP markitdown

Call the `convert_to_markdown` MCP tool with the document URI.
See `modules/uri-construction.md` for URI formatting rules.

If the tool is available and succeeds, you have the best
possible conversion. Proceed to the SANITIZE step.

If the tool is not available (not found, connection error)
or fails, proceed to Tier 2.

### Tier 2: Native Claude Code Tools

Use built-in tools as format-specific fallbacks.
See `modules/fallback-tiers.md` for per-format instructions.

**Supported in Tier 2**: PDF, HTML, images, CSV, JSON, XML.
**Not supported in Tier 2**: DOCX, PPTX, XLSX, audio,
archives, e-books. Proceed to Tier 3 for these.

### Tier 3: User Notification

When neither Tier 1 nor Tier 2 can handle the format:

> I cannot convert this {format} file without the markitdown
> MCP server. To enable conversion, add this to `.mcp.json`:
>
> ```json
> {
>   "mcpServers": {
>     "markitdown": {
>       "type": "stdio",
>       "command": "uvx",
>       "args": ["markitdown-mcp"]
>     }
>   }
> }
> ```
>
> Alternatively, convert the file to PDF or HTML first,
> which I can read with built-in tools.

### SANITIZE Step

All converted content is external. Apply the
`leyline:content-sanitization` checklist:

- Size check (truncate sections over 2000 words)
- Strip system/instruction tags
- Wrap in external content boundary markers

## Integration

Consumer skills depend on this skill and reference the
protocol by name:

```yaml
dependencies:
- leyline:document-conversion
```

Then in their workflow: "Convert the document using the
`leyline:document-conversion` protocol."

## Detailed References

- Format support details: `modules/format-matrix.md`
- Per-format fallback instructions: `modules/fallback-tiers.md`
- URI construction rules: `modules/uri-construction.md`