docx-mcp

Legal document redlining engine. Takes AI-generated changes (structured JSON) and applies them as professional tracked changes with comments inside .docx files. The output is indistinguishable from what a lawyer would produce in Microsoft Word -- proper w:ins/w:del markup, comment annotations with justification text, and preserved formatting.

Installation

Requires Python 3.14+.

uv sync

Related MCP server: MCP-OPENAPI-DOCX

Quick start

Python API

from docx_mcp import (
    ParagraphChange, ParagraphChangeType,
    TableChange, TableChangeType,
    RedlineConfig, apply_redlines,
)

changes = [
    # Modify a body paragraph
    ParagraphChange(
        kind="paragraph",
        fragment_id="3",              # ← str (was int in v0.1.0)
        change_type=ParagraphChangeType.MODIFY,
        new_text="The Company **shall** provide written notice.",
        justification="Strengthened obligation language.",
    ),
    # Delete a paragraph
    ParagraphChange(
        kind="paragraph",
        fragment_id="5",
        change_type=ParagraphChangeType.DELETE,
        justification="Removed redundant clause.",
    ),
    # Append a new paragraph
    ParagraphChange(
        kind="paragraph",
        fragment_id="7",
        change_type=ParagraphChangeType.APPEND_AFTER,
        new_text="The foregoing shall survive termination.",
        justification="Added survival provision.",
    ),
    # Modify a header paragraph
    ParagraphChange(
        kind="paragraph",
        fragment_id="header_1.1",
        change_type=ParagraphChangeType.MODIFY,
        new_text="CONFIDENTIAL",
        justification="Updated header text.",
    ),
    # Modify a table cell
    TableChange(
        kind="table",
        table_id=2,
        row=1,
        col=1,
        change_type=TableChangeType.MODIFY_CELL,
        new_text="Updated **cell** content",
        justification="Corrected table entry.",
    ),
    # Clear a table cell
    TableChange(
        kind="table",
        table_id=2,
        row=3,
        col=2,
        change_type=TableChangeType.CLEAR_CELL,
        justification="Removed obsolete data.",
    ),
]

doc = apply_redlines("contract.docx", changes)
doc.save("contract_redlined.docx")

CLI

# Extract fragment text from a document
docx-mcp convert input.docx
docx-mcp convert input.docx --format json

# Apply changes
docx-mcp apply input.docx changes.json -o output.docx

# Validate a redlined document
docx-mcp validate output.docx

# Audit a document for structural issues
docx-mcp audit input.docx
docx-mcp audit input.docx --format json

Note: The CLI convert command extracts body content only (no headers, footers, or tables). For full-document extraction, use the MCP extract_fragments tool or the Python full_to_fragments() function.

MCP server

The library includes an MCP server so that LLM clients (Claude Desktop, Cursor, etc.) can redline .docx files directly.

# Start the server (stdio transport)
docx-mcp-server

Configure in Claude Desktop (claude_desktop_config.json):

{
  "mcpServers": {
    "docx-mcp": {
      "command": "uv",
      "args": ["run", "--directory", "/path/to/docx-mcp", "docx-mcp-server"]
    }
  }
}

Configure in Cursor (.cursor/mcp.json):

{
  "mcpServers": {
    "docx-mcp": {
      "command": "uv",
      "args": ["run", "--directory", "/path/to/docx-mcp", "docx-mcp-server"]
    }
  }
}

Tools

Resource

Example workflow

An LLM client would typically:

1. Call extract_fragments to read the document and get fragment IDs.

2. Reason about the content and construct a list of changes.

3. Call apply_changes with the change list to produce a redlined document.

4. Optionally call diff_fragments to compare original vs. redlined output.

Concepts

Fragments

Documents are decomposed into fragments: paragraphs, tables, headers, and footers, all indexed in document order. Each fragment has a string ID.

Fragment IDs:

Tables and body paragraphs share the same ID space (they interleave in document order). Fragment "3" might be a table and fragment "4" a paragraph.

Use extract_fragments (MCP) or full_to_fragments() (Python) to see the fragment map for any document:

<f=1>Introduction paragraph.</f=1>
<f=2>**Definitions.** The following terms shall apply.</f=2>
<table=3 rows=2 cols=3>
<cell=3.1.1 span="2">Merged Header</cell=3.1.1>
<cell=3.1.3>Header C</cell=3.1.3>
<cell=3.2.1>Data 1</cell=3.2.1>
<cell=3.2.2>Data 2</cell=3.2.2>
<cell=3.2.3>Data 3</cell=3.2.3>
</table=3>
<f=4>Closing paragraph. See [Section 2](https://example.com).</f=4>
<f=header_1.1>Confidential</f=header_1.1>
<f=footer_1.1>Page 1 of 10</f=footer_1.1>

Tables

Simple tables

Simple (rectangular) tables are extracted as <table=N> blocks. Each cell has a cell_id in "table_id.row.col" format (e.g., "3.1.2").

Merged-cell tables

Tables with horizontally or vertically merged cells (gridSpan / vMerge) are now supported. Merge spans are shown as attributes:

• span="2" — cell spans 2 columns (horizontal merge)

• vspan="3" — cell spans 3 rows (vertical merge)

Spanned-over cells (positions covered by a merge) are omitted from output. For example, if cell=3.1.1 has span="2", then cell=3.1.2 does not appear.

When targeting merged cells with changes, always target the originating cell (the one with the span/vspan attribute). Targeting a spanned-over position raises a ValueError.

Skipped tables

Tables that cannot be processed (nested tables, malformed merges, tables inside headers/footers) appear as:

<table=5 skipped reason="table 5, cell 2.3 contains nested table"/>

Headers and footers

Header and footer paragraphs are extracted with prefixed fragment IDs: header_1.1, footer_2.1, etc. The first number is the 1-based part index (usually 1 for the default header/footer), the second is the 1-based paragraph index within that part.

Header/footer paragraphs can be modified, deleted, and appended to just like body paragraphs. Tables inside headers/footers are not editable and are reported as skipped elements.

Limitation: Comments on header/footer changes are not attached to the output (Word and LibreOffice do not support comment ranges in those parts). They trigger a UserWarning and are dropped.

Hyperlinks

Hyperlinks are extracted as [link text](url) inline within paragraph text. Formatting inside links is preserved: [**bold link**](url).

When modifying an existing paragraph, [text] without (url) preserves the original hyperlink URL. [text](new_url) creates a new link.

When appending new text, [text](url) creates a hyperlink. [text] without (url) produces plain text — always specify (url) on append if you want a hyperlink.

Tracked changes policy

Documents with pre-existing tracked changes (<w:ins>, <w:del>, <w:moveFrom>, <w:moveTo>) are hard-rejected in both extract_fragments and apply_redlines. Accept or reject all changes in Word before processing.

collapse_empty mode

Optional mode that suppresses empty paragraphs from extraction and redlining. Produces cleaner output for LLM consumption. When enabled, it must be used consistently across extraction and redlining — mismatched values cause fragment ID misalignment.

Change types

Paragraph changes

Table cell changes

Cell modification uses positional alignment: if the cell has multiple paragraphs, the new text is split on newlines (\n) and each line is applied to the corresponding paragraph in order. Cell content is marked with tracked changes and comments just like paragraph modifications.

Blank line management

When appending new paragraphs, you can control surrounding blank lines:

Change(
    fragment_id=10,
    change_type=ChangeType.APPEND_AFTER,
    new_text="New clause text here.",
    justification="Added new provision.",
    blank_lines_before=1,  # Insert 1 blank line before the new paragraph
    blank_lines_after=1,   # Insert 1 blank line after the new paragraph
)

When deleting paragraphs, you can remove trailing blank lines automatically:

Change(
    fragment_id=15,
    change_type=ChangeType.DELETE,
    justification="Removed obsolete clause.",
    delete_next_blanks=1,  # Also delete the next blank paragraph
)

All blank lines are marked as tracked insertions/deletions and will appear in the redlined document.

Pseudo-Markdown

Text content uses a simplified Markdown-like format for inline formatting:

• **bold**

• _italic_

• __underline__

Unicode characters (smart quotes, em dashes, section symbols, non-breaking spaces) are preserved as-is.

Font inheritance: When appending new paragraphs, the font family, size, and color are automatically copied from the reference paragraph's first text-bearing run. Bold, italic, and underline formatting from the pseudo-Markdown is layered on top of the inherited base formatting.

Changes JSON

The CLI accepts a JSON file containing either a bare array or a {"changes": [...]} wrapper.

Paragraph changes example

[
  {
    "fragment_id": "1",
    "change_type": "modify",
    "new_text": "The Seller agrees to deliver within **sixty** days.",
    "justification": "Extended delivery window."
  },
  {
    "fragment_id": "3",
    "change_type": "delete",
    "justification": "Removed governing law clause.",
    "delete_next_blanks": 1
  },
  {
    "fragment_id": "5",
    "change_type": "append_after",
    "new_text": "This Agreement shall be governed by Delaware law.",
    "justification": "Added Delaware governing law.",
    "blank_lines_before": 1,
    "blank_lines_after": 0
  },
  {
    "fragment_id": "header_1.1",
    "change_type": "modify",
    "new_text": "CONFIDENTIAL",
    "justification": "Updated header marking."
  }
]

Table cell changes example

[
  {
    "cell_id": "2.1.1",
    "change_type": "modify_cell",
    "new_text": "Updated **cell** content",
    "justification": "Corrected cell value."
  },
  {
    "cell_id": "2.3.2",
    "change_type": "clear_cell",
    "justification": "Cleared obsolete data."
  }
]

Cell IDs use the format "table_id.row.col" where rows and columns are 1-based.

Validation

The validate_document() function (and docx-mcp validate CLI) checks:

• Annotation ID isolation -- tracked-change and comment IDs don't collide across groups

• Comment integrity -- every <w:comment> has matching range markers in the document body, and vice versa

• Tracked-change attributes -- every <w:ins> and <w:del> has required w:id, w:author, and w:date

• Package consistency -- content-type and relationship entries exist for comments.xml

from docx_mcp import validate_document

result = validate_document(doc)
if not result.ok:
    for error in result.errors:
        print(error)

Architecture

The library manipulates OOXML directly via lxml (not python-docx) because python-docx has no tracked-change support. Key design decisions:

• Word-level diffing via diff-match-patch with a word-to-char mapping for high-quality diffs

• Conservative mutation -- only changed paragraphs are touched; everything else passes through byte-identical

• Globally unique annotation IDs via a monotonic IdManager seeded from the document's existing max ID

• python-docx is used only for test fixture generation, not in the library itself

Module map

src/docx_mcp/
  __init__.py        Public API
  cli.py             CLI entry point (apply, convert, validate)
  models.py          Pydantic data models (Change, ChangeType, RedlineConfig, ...)
  document.py        DocxDocument: ZIP parsing, XML tree access, serialization
  converter.py       Paragraph & table XML -> pseudo-Markdown conversion
  table_utils.py     Table inspection utilities (cell access, simplicity checks)
  tokenizer.py       Word-level tokenization
  differ.py          Word-level diff engine (diff-match-patch wrapper)
  run_ops.py         Diff-to-XML-run mapping, run splitting, element building
  id_manager.py      Monotonic annotation ID allocator
  comments.py        Comment creation and range marker insertion
  redliner.py        Main orchestrator: apply_redlines()
  table_redliner.py  Table cell change application
  audit.py           Document structural audit (headers, images, tables, etc.)
  validator.py       Structural validation checks
  server.py          MCP server (FastMCP 3.x, stdio transport)
  handlers/
    modify.py        Word-level tracked changes on existing paragraphs
    delete.py        Full paragraph deletion markup
    append.py        New paragraph insertion markup

Development

# Run tests
uv run pytest tests/ -v

# Lint
uvx ruff check src/ tests/

# Auto-fix lint issues
uvx ruff check src/ tests/ --fix

# Type check
uvx ty check src/ tests/

431 tests covering all modules, handlers, table operations, headers/footers, hyperlinks, tracked-change rejection, merged-cell tables, section breaks, CLI, validation, and MCP server.

License

MIT