WriteBetter MCP Extension

A Claude Desktop extension (MCP server) that connects Claude to the WriteBetter macOS app running on the same Mac. Claude can work with your local WriteBetter library: commands, the Prompt Library, context folders, run history and usage stats.

Everything stays on your machine. The extension only talks to WriteBetter over 127.0.0.1:51515.

Requirements

• macOS with the WriteBetter app installed and running (download: https://svenbadalyan.com/tools/)

• Claude Desktop

Related MCP server: LiteFarm MCP Server

Install

1. In WriteBetter, open Settings and turn on AI Assistant Integration. Keep the app running.

2. Download writebetter.mcpb from this repository.

3. Open Claude Desktop → Settings → Extensions → Advanced settings → Install Extension… and select the downloaded file.

4. Ask Claude, for example:

   • "List my WriteBetter commands."

   • "Create a WriteBetter command called de that translates English text into German and keeps the tone."

   • "Show me the run history of my de command and suggest how to improve its prompt."

How it works

• WriteBetter listens on 127.0.0.1:51515 (loopback only, never the network), and only while AI Assistant Integration is turned on.

• index.js is the MCP server. Each tool call opens a short TCP connection to that port, sends one JSON line, and relays the JSON response back.

• Every call goes through WriteBetter's own validation (duplicate names, chain rules, value ranges), exactly as in the app.

• Safety switches (WriteBetter → Settings → AI Assistant Integration):

  • Ask before deleting or running (on by default): every delete/clear tool and run_command shows an Allow / Deny dialog in WriteBetter and waits up to 90 s for an answer (Deny is the default button).

  • Read-only: only the read tools work; everything else is refused.

Build from source

npm install
npm run build:mcpb   # produces writebetter.mcpb

Manual alternative without the extension: add this to ~/Library/Application Support/Claude/claude_desktop_config.json and restart Claude Desktop (use only one of the two methods):

"mcpServers": {
  "writebetter": {
    "command": "node",
    "args": ["/absolute/path/to/writebetter-mcp-extension/index.js"]
  }
}

Tools exposed

Tools marked ⚠︎ ask for approval in WriteBetter first (unless turned off).

General: get_status, search_history, get_usage_stats

Commands: list_commands (filters: include_inactive, type), get_command (by id or shortcut, with settings and prompt structure), match_command (best match for a phrase, with scores), create_command, update_command, update_command_settings (model, temperature, reasoning, retries, generation mode, saved-history size), set_command_active (inactive commands appear in the app's Commands tab behind the eye button), get_command_history, ⚠︎ clear_command_history, ⚠︎ delete_command, ⚠︎ run_command (runs on the user's API keys and is saved to history)

Prompts: list_prompts (filters: query, tag), get_prompt (by id or name), create_prompt, update_prompt, ⚠︎ delete_prompt

Context folders: list_context_folders, get_context_folder, get_active_context, create_context_folder (does not change the active folder unless make_active: true), rename_context_folder, select_context_folder, add_context_snippet, update_context_snippet, ⚠︎ delete_context_snippet, ⚠︎ clear_context_folder, ⚠︎ delete_context_folder, set_context_enabled, list_context_labels, create_context_label, ⚠︎ delete_context_label

Image snippets are listed by file name only; image data is not sent.

Troubleshooting

If a tool call fails with "Could not reach WriteBetter on 127.0.0.1:51515", the app either isn't running or the toggle in Settings is off. After updating WriteBetter or this extension, make sure both are the new version: an older app answers new tools with "Unknown action".

Privacy Policy

This extension only talks to the WriteBetter app running on the same Mac, over 127.0.0.1:51515. It makes no other network connections, collects no telemetry, and sends nothing to WriteBetter or any third party. Commands, prompts, context, run history and usage data stay in WriteBetter's local storage.

Full policy:

• English: https://svenbadalyan.com/writebetter/privacy/

• Deutsch: https://svenbadalyan.com/de/writebetter/privacy/

Support

contact@svenbadalyan.com

License

MIT, see LICENSE. The license covers this extension only; the WriteBetter app itself is a separate product.