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Safety model

Glyphs MCP is designed for human-controlled font editing. The server gives agents useful tools, but the workflow should keep you in charge of target selection, mutation, review, and saving.

Core rules​

  • Read before write: inspect current state before changing it.
  • Confirm targets: name the font, master, glyph, layer, path, or selected nodes before mutation.
  • Dry run before apply: preview changes when the tool supports dry_run.
  • Confirm-gated mutations: use confirm=true only after approval.
  • No auto-save: the plug-in does not save fonts unless save_font is called.
  • Prefer dedicated tools: use specific tools before free-form code.

Safe prompt template​

Use this when you want the agent to review first and mutate only after approval:

You are my Glyphs MCP assistant.

Rules:
- Read current state before any mutation.
- Confirm exact targets before changing anything.
- Never auto-save.
- Never mutate without a dry run first when the tool supports dry_run.
- Show me a short summary of proposed changes: counts, biggest deltas, and skipped items.
- Wait for me to reply exactly "apply" before calling any tool with confirm=true.

Task: <describe the goal>

1. Inspect current state with read-only tools.
2. Run the appropriate apply tool with dry_run=true.
3. Stop and wait for approval.
4. If I reply "apply", run the same call again with confirm=true.
5. If I reply "save", call save_font.

Local access​

By default, Glyphs MCP binds to localhost and does not require authentication. Keep it local unless you understand the security implications of exposing it elsewhere.

Optional controls:

  • GLYPHS_MCP_AUTH_TOKEN: require a static token on requests.
  • GLYPHS_MCP_ALLOWED_ORIGINS: restrict request origins by hostname allowlist.

See Settings for the exact environment variables.

What safety does not replace​

Glyphs MCP can make repeatable tool calls, but it does not replace type-design judgement. Always proof kerning, spacing, feature behavior, and outline edits visually in Glyphs before saving or shipping.