AI agents call measure_stems to retrieve information from Glyphs without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
Measuring stems in a font design context retrieves dimensional data about glyph strokes without modifying or executing operations that could alter the design. This is consistent with sibling analysis tools that inspect font properties. While the description is empty, the naming pattern and server context strongly suggest read-only inspection.
From the tool's definition Tool name 'measure_stems' combined with sibling tools like 'analyze_kerning', 'analyze_spacing', and 'check_*' functions all appear to be font analysis/inspection tools.
Documented attack patterns abuse exactly the kind of access measure_stems gives an agent:
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 measure_stems:
{
"version": "1",
"default": "deny",
"tools": {
"measure_stems": {}
}
}measure_stems is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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measure_stems. It is categorised as a Read tool in the Glyphs MCP Server, which means it retrieves data without modifying state.
Register the Glyphs MCP server in PolicyLayer and add a rule for measure_stems: 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.
measure_stems is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the measure_stems 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.
Set action: deny in the PolicyLayer policy for measure_stems. 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.
measure_stems 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.
Start from Glyphs, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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41 Glyphs tools catalogued and risk-classified — across an index of 43,000+ MCP servers.