Rename a glyph. Fails if new_name already exists.
AI agents use rename_glyph to create or update resources in Glyphs — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Glyphs environment.
Renaming a glyph is a reversible modification operation: the old name can be restored, and the change does not destroy data or execute arbitrary code. It falls squarely in the Write category.
From the tool's definition Tool description states 'Rename a glyph' — a rename operation modifies metadata associated with an existing glyph in the font data structure. The server is explicitly designed for 'read and write font data directly in GlyphsApp.'
Documented attack patterns abuse exactly the kind of access rename_glyph 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 rename_glyph:
{
"version": "1",
"default": "deny",
"tools": {
"rename_glyph": {
"limits": [
{
"counter": "rename_glyph_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}rename_glyph stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Rename a glyph. Fails if new_name already exists. It is categorised as a Write tool in the Glyphs MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Glyphs MCP server in PolicyLayer and add a rule for rename_glyph: 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.
rename_glyph is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the rename_glyph 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 rename_glyph. 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.
rename_glyph 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.