Glyphs MCP

Site: https://ap.cx/gmcp

A Model Context Protocol server for Glyphs that exposes font‑specific tools to AI/LLM agents.

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Quick install (interactive):

python3 install.py

On macOS Finder you can also double‑click RunInstall.command in the repo root; it launches the same installer (python3 install.py). If Gatekeeper blocks it, right‑click → Open once to approve.

What Is an MCP Server?

A Model Context Protocol server is a lightweight process that:

1. Registers tools (JSON‑RPC methods) written in the host language (Python here).
2. Streams JSON output back to the calling agent.

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Command Set (v0.3)

Tool	Description
list_open_fonts	List all open fonts and basic metadata.
get_font_glyphs	Return glyph list and key attributes for a font.
get_font_masters	Detailed master information for a font.
get_font_instances	List instances and their interpolation data.
get_glyph_details	Full glyph data including layers, paths, components.
get_font_kerning	All kerning pairs for a given master.
create_glyph	Add a new glyph to the font.
delete_glyph	Remove a glyph from the font.
update_glyph_properties	Change unicode, category, export flags, etc.
copy_glyph	Duplicate outlines / components from one glyph to another.
update_glyph_metrics	Adjust width and side‑bearings.
get_glyph_components	Inspect components used in a glyph.
add_component_to_glyph	Append a component to a glyph layer.
add_anchor_to_glyph	Add an anchor to a glyph layer.
set_kerning_pair	Set or remove a kerning value.
get_selected_glyphs	Info about glyphs currently selected in UI.
get_selected_font_and_master	Current font + master and selection snapshot.
get_selected_nodes	Detailed selected nodes with per‑master mapping for edits.
get_glyph_paths	Export paths in a JSON format suitable for LLM editing.
set_glyph_paths	Replace glyph paths from JSON.
ExportDesignspaceAndUFO	Export designspace/UFO bundles with structured logs and errors.
execute_code	Execute arbitrary Python in the Glyphs context.
execute_code_with_context	Execute Python with injected helper objects.
save_font	Save the active font (optionally to a new path).

execute_code and execute_code_with_context accept an optional timeout in seconds. Calls default to 60 s, and the bridge honours any larger per-call value you provide.

ExportDesignspaceAndUFO

Kick off a headless export of UFO masters and designspace documents directly from the MCP server. The tool returns absolute paths to generated files along with the exporter log so clients can surface progress in real time. Debug lines are prefixed with [ExportDesignspaceAndUFO DEBUG] and include helpful context about axis mappings, temporary folders, and file moves.

Failures now yield rich diagnostics instead of a bare string. In addition to error, the payload includes errorType, a formatted traceback, and contextual details about the font and options that triggered the exception. Use these fields to surface actionable feedback or drive automated retries without guessing what went wrong.

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Install & Setup

Recommended (simplest): run the one‑command interactive installer. It handles Python setup, dependencies, and placing the plug‑in where Glyphs expects it.

python3 install.py

Alternatively, you can install the plug‑in manually as described below.

Install the Plug‑in

Copy or create a symlink of src/glyphs-mcp/Glyphs MCP.glyphsPlugin into ~/Library/Application Support/Glyphs 3/Plugins/, then restart Glyphs.

After regenerating the ObjectWrapper documentation, refresh the bundled copy with:

python src/glyphs-mcp/scripts/copy_documentation.py

To start the Glyphs MCP server, open the Edit menu and choose Start MCP Server.

The server will be available at http://127.0.0.1:9680/ using MCP Streamable HTTP transport.

Open the Macro Panel to access the console.

One‑Command Installer (Interactive)

Prefer a guided setup? Run the interactive installer to:

• choose Glyphs’ Python or a custom Python,
• install dependencies in the appropriate location, and
• copy the plug‑in into the Glyphs Plugins folder.

python3 install.py

What the installer does

• Detects available Python 3 interpreters (prefers 3.12+, python.org builds).
• Installs Python dependencies either into Glyphs’ own Python or your user site‑packages.
• Installs the plug‑in into ~/Library/Application Support/Glyphs 3/Plugins/ by copy (recommended) or symlink (dev).
• Verifies imports and offers tips if something fails (e.g., Apple Silicon wheels, cache issues).

Step‑by‑step flow and choices

1. Choose Python environment

   • Option 1: Glyphs’ Python (Plugin Manager)
     • Recommended default if you installed “Python” in Glyphs → Settings → Addons.
     • The installer uses Glyphs’ pip and installs into ~/Library/Application Support/Glyphs 3/Scripts/site-packages.
     • If not found, it tells you to install “GlyphsPythonPlugin” in Glyphs and re‑run.
   • Option 2: Custom Python (python.org / Homebrew)
     • Recommended: python.org 3.12+ on macOS. On Apple Silicon, use native arm64 (avoid Rosetta).
     • The installer lists detected interpreters (python.org, Homebrew, PATH). Pick one or enter a path.
     • If version < 3.12, you’ll be warned and can abort to install a newer Python.

2. Install dependencies

   • Glyphs’ Python: installs with Glyphs’ pip into the Glyphs Scripts site‑packages.
   • Custom Python: runs <python> -m pip install --user -r requirements.txt (no sudo).
   • If imports fail, it suggests retrying with --no-cache-dir --force-reinstall and gives the exact command. On Apple Silicon, ensure wheels match the CPU architecture.

3. Install the plug‑in

   • Option 1: Copy (default, recommended)
     • Copies src/glyphs-mcp/Glyphs MCP.glyphsPlugin into ~/Library/Application Support/Glyphs 3/Plugins/.
   • Option 2: Link (symlink; for development)
     • Useful if you plan to edit this repo and test changes live.
   • If a plug‑in already exists, you’ll be prompted to replace it.

4. Finish and start the server in Glyphs

   • Open Glyphs → Edit → Start MCP Server.
   • The server runs at http://127.0.0.1:9680/ with MCP Streamable HTTP transport.
   • The installer can optionally show client setup snippets for popular tools (Claude Desktop, Claude Code, Continue, Cursor, Windsurf, Codex). It uses either npx mcp-remote or the Python mcp-proxy if on PATH.

Tips

• If you’re unsure, accept the defaults: “Glyphs’ Python” and “Copy”.
• Prefer python.org 3.12+ over Homebrew for fewer compatibility surprises on macOS.
• On Apple Silicon, avoid Rosetta‑translated Pythons and ensure pip installs arm64 wheels.
• No sudo is required; everything installs into your user directories.

Build Site Images (WebP)

Docs use a splash image at /images/glyphs-app-mcp/glyphs-mcp.webp.

• Requirements: Node 20+ and the sharp package (npm i sharp).
• Convert PNG assets from content/images/glyphs-app-mcp to WebP in public/images/glyphs-app-mcp:

node scripts/convert-images.mjs

The script ensures glyphs-mcp.webp (the hero image for the doc) is generated, then converts the rest.

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Contributing

PRs and feedback are welcome.

Contributors

• Thierry Charbonnel (@thierryc) — Author
• Florian Pircher (@florianpircher)
• Georg Seifert (@schriftgestalt)
• Jeremy Tribby (@jpt)

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