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Claude Desktop Commander MCP

write_file

Destructive

Write or append content to files. Supports text, Excel, and DOCX formats with chunking for large files.

Instructions

                    Write or append to file contents.

                    IMPORTANT: DO NOT use this tool to create PDF files. Use 'write_pdf' for all PDF creation tasks.
                    DO NOT use this tool to edit DOCX files. Use 'edit_block' with old_string/new_string instead.
                    To CREATE a new DOCX, use write_file with .docx extension — text content with markdown headings (#, ##, ###) is converted to styled DOCX paragraphs.

                    CHUNKING IS STANDARD PRACTICE: Always write files in chunks of 25-30 lines maximum.
                    This is the normal, recommended way to write files - not an emergency measure.

                    STANDARD PROCESS FOR ANY FILE:
                    1. FIRST → write_file(filePath, firstChunk, {mode: 'rewrite'})  [≤30 lines]
                    2. THEN → write_file(filePath, secondChunk, {mode: 'append'})   [≤30 lines]
                    3. CONTINUE → write_file(filePath, nextChunk, {mode: 'append'}) [≤30 lines]

                    ALWAYS CHUNK PROACTIVELY - don't wait for performance warnings!

                    WHEN TO CHUNK (always be proactive):
                    1. Any file expected to be longer than 25-30 lines
                    2. When writing multiple files in sequence
                    3. When creating documentation, code files, or configuration files

                    HANDLING CONTINUATION ("Continue" prompts):
                    If user asks to "Continue" after an incomplete operation:
                    1. Read the file to see what was successfully written
                    2. Continue writing ONLY the remaining content using {mode: 'append'}
                    3. Keep chunks to 25-30 lines each

                    FORMAT HANDLING (by extension):
                    - Text files: String content
                    - Excel (.xlsx, .xls, .xlsm): JSON 2D array or {"SheetName": [[...]]}
                      Example: '[["Name","Age"],["Alice",30]]'

                    Files over 50 lines will generate performance notes but are still written successfully.
                    Only works within allowed directories.

                    IMPORTANT: Always use absolute paths for reliability. Paths are automatically normalized regardless of slash direction. Relative paths may fail as they depend on the current working directory. Tilde paths (~/...) might not work in all contexts. Unless the user explicitly asks for relative paths, use absolute paths.
                    This command can be referenced as "DC: ..." or "use Desktop Commander to ..." in your instructions.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
pathYes
contentYes
modeNorewrite
Behavior5/5

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

Annotations indicate destructive hint and not read-only, which description confirms and adds context about chunking, performance notes for large files, allowed directories, path normalization, and formatting for various file types. No contradictions.

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

Conciseness3/5

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

The description is verbose (over 400 words) with repeated chunking instructions. While well-structured with sections and bullet points, it could be more concise without losing key information.

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

Completeness4/5

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

Covers most aspects: purpose, when to use, chunking, format handling, path requirements, and continuation. Missing explicit return value description (no output schema), but otherwise complete for a write operation with destructive hint.

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 has 0% description coverage, so the description carries the burden. It explains content formatting for Excel and DOCX but does not systematically describe each parameter (e.g., path format, mode enum). Partial compensation but incomplete.

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?

Description clearly states 'Write or append to file contents' and distinguishes from siblings like write_pdf and edit_block by specifying when to use each. The verb-resource pair is precise and unambiguous.

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?

Explicitly provides when to use (creating new files, appending) and when not to use (PDFs, editing DOCX), including alternative tools. Gives step-by-step process with chunking and continuation handling.

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

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