get_masters

THE RISK

Low Risk

Why get_masters needs a policy

This tool retrieves metadata about font masters (metrics and axis positions) without modifying, deleting, or executing anything. It is a read-only query operation with no side effects. Severity is low because the data retrieved is design metadata non-sensitive in nature, with no destructive or financial impact.

From the tool's definition Tool name is 'get_masters' and description states 'Get all font masters' — the verb 'Get' and lack of any modification language indicate a retrieval operation.

Documented attack patterns abuse exactly the kind of access get_masters gives an agent:

POLICY

How to control get_masters

PolicyLayer is an MCP gateway — it sits between your AI agents and Glyphs, and nothing reaches the server without passing your rules. This is the rule we recommend for get_masters:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "get_masters": {}
  }
}

get_masters is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

Create a free account and register Glyphs — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More Glyphs tools

Destructive delete_glyph Delete a glyph from the font. This cannot be undone via MCP. Destructive delete_kerning_pair Delete a kerning pair. Execute execute_in_glyphs execute_in_glyphs Execute rmx_scale rmx_scale Write duplicate_glyph Duplicate a glyph (all layers and paths) under a new name. Write create_glyph create_glyph Write rename_glyph Rename a glyph. Fails if new_name already exists. Write set_feature_code Create or update an OpenType feature.

All 41 Glyphs tools →

Read tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about get_masters

What does the get_masters tool do? +

Get all font masters with their metrics and axis positions. It is categorised as a Read tool in the Glyphs MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on get_masters? +

Register the Glyphs MCP server in PolicyLayer and add a rule for get_masters: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Glyphs. Nothing to install.

What risk level is get_masters? +

get_masters is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit get_masters? +

Yes. Add a rate_limit block to the get_masters rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block get_masters completely? +

Set action: deny in the PolicyLayer policy for get_masters. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides get_masters? +

get_masters is provided by the Glyphs MCP server (nmassi/glyphs-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Glyphs tool call.

Start from Glyphs, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →