Send an emoji reaction to a Crow contact.
AI agents use crow_react to create or update resources in Crow — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Crow environment.
Sending an emoji reaction is a reversible write operation that creates or adds data to a communication context. It does not execute arbitrary operations, delete data irreversibly, move money, or merely read information. The low severity reflects the minimal blast radius: an AI agent could spam reactions but cannot cause significant harm to the project management system or its data.
From the tool's definition Tool description states it will 'Send an emoji reaction to a Crow contact' — this creates a reaction object/message that modifies the state of a conversation or collaboration record.
Documented attack patterns abuse exactly the kind of access crow_react gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Crow, and nothing reaches the server without passing your rules. This is the rule we recommend for crow_react:
{
"version": "1",
"default": "deny",
"tools": {
"crow_react": {
"limits": [
{
"counter": "crow_react_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}crow_react 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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Send an emoji reaction to a Crow contact. It is categorised as a Write tool in the Crow MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Crow MCP server in PolicyLayer and add a rule for crow_react: 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 Crow. Nothing to install.
crow_react 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 crow_react 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 crow_react. 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.
crow_react is provided by the Crow MCP server (kh0pper/crow). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Crow, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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576 Crow tools catalogued and risk-classified — across an index of 43,000+ MCP servers.