AI agents invoke play_emotion to trigger actions in Reachy Mini MCP Server. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
Based on the server context (Reachy Mini robot control) and sibling tools like 'dance', 'move_head', and 'speak', 'play_emotion' most likely triggers a physical robot animation or expression sequence. This constitutes executing an external operation on physical hardware. Confidence is reduced due to the empty description. Severity is medium as misuse could cause unexpected robot movements in physical space.
From the tool's definition Tool name 'play_emotion' on a robot control server; description is empty and uninformative.
Documented attack patterns abuse exactly the kind of access play_emotion gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Reachy Mini MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for play_emotion:
{
"version": "1",
"default": "deny",
"tools": {
"play_emotion": {
"limits": [
{
"counter": "play_emotion_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}play_emotion stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
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play_emotion. It is categorised as a Execute tool in the Reachy Mini MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Reachy Mini MCP Server MCP server in PolicyLayer and add a rule for play_emotion: 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 Reachy Mini MCP Server. Nothing to install.
play_emotion is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the play_emotion 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 play_emotion. 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.
play_emotion is provided by the Reachy Mini MCP Server MCP server (pixelml/reachy-mini-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Reachy Mini MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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8 Reachy Mini MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.