Create a new Hearts game. You sit South against 3 AI opponents (North, East, West).
Part of the Hearts server.
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AI agents use create_game to create or modify resources in Hearts. Write operations carry medium risk because an autonomous agent could trigger bulk unintended modifications. Rate limits prevent a single agent session from making hundreds of changes in rapid succession. Argument validation ensures the agent passes expected values.
Without a policy, an AI agent could call create_game repeatedly, creating or modifying resources faster than any human could review. PolicyLayer's rate limiting ensures write operations happen at a controlled pace, and argument validation catches malformed or unexpected inputs before they reach Hearts.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"create_game": {
"limits": [
{
"counter": "create_game_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Hearts policy for all 8 tools.
These attack patterns abuse exactly the kind of access create_game gives an agent. Each links to the full case and the policy that stops it:
Other write tools across the catalogue. The same approach applies to each: rate-limit and validate the arguments.
Create a new Hearts game. You sit South against 3 AI opponents (North, East, West).. It is categorised as a Write tool in the Hearts MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Hearts MCP server in PolicyLayer and add a rule for create_game: 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 Hearts. Nothing to install.
create_game 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 create_game 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 create_game. 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.
create_game is provided by the Hearts MCP server (hearts-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 8 Hearts tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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