AI agents call stackchan_face as a supporting operation in Stackchan workflows.
The tool name suggests it controls facial expressions on the Stack-chan robot. Based on the server description mentioning 'facial expressions', this likely sends display/animation commands to a physical robot's face. This is an Execute-level action (triggers external hardware operation), but with an empty description, confidence is low.
From the tool's definition Tool name 'stackchan_face' and empty description; server description mentions 'facial expressions' as one capability
Documented attack patterns abuse exactly the kind of access stackchan_face gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Stackchan, and nothing reaches the server without passing your rules. This is the rule we recommend for stackchan_face:
{
"version": "1",
"default": "deny",
"tools": {
"stackchan_face": {
"limits": [
{
"counter": "stackchan_face_rate",
"window": "minute",
"max": 60,
"scope": "grant"
}
]
}
}
}stackchan_face gets a rate cap, and everything else on the server is denied unless you say otherwise.
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stackchan_face. It is categorised as a Other tool in the Stackchan MCP Server, which means it performs auxiliary operations.
Register the Stackchan MCP server in PolicyLayer and add a rule for stackchan_face: 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 Stackchan. Nothing to install.
stackchan_face is a Other tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the stackchan_face 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 stackchan_face. 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.
stackchan_face is provided by the Stackchan MCP server (migratorywhale/stackchan-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Stackchan, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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12 Stackchan tools catalogued and risk-classified — across an index of 43,000+ MCP servers.