Send a heartbeat signal from a device to report its status. WHEN TO USE: - Regular device health monitoring (every 30-60 seconds) - Reporting current playback status - Reporting errors or issues RETURNS: - success: Boolean indicating success - device_status: Current device status in system - next...
Risk signalsBulk/mass operation — affects multiple targets
Part of the Trillboards DOOH Advertising server.
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AI agents use device_heartbeat to create or modify resources in Trillboards DOOH Advertising. 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 device_heartbeat 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 Trillboards DOOH Advertising.
Write tools can modify data. A rate limit prevents runaway bulk operations from AI agents.
{
"version": "1",
"default": "deny",
"tools": {
"device_heartbeat": {
"limits": [
{
"counter": "device_heartbeat_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}See the full Trillboards DOOH Advertising policy for all 74 tools.
These attack patterns abuse exactly the kind of access device_heartbeat 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.
Send a heartbeat signal from a device to report its status. WHEN TO USE: - Regular device health monitoring (every 30-60 seconds) - Reporting current playback status - Reporting errors or issues RETURNS: - success: Boolean indicating success - device_status: Current device status in system - next_heartbeat_seconds: Recommended interval for next heartbeat EXAMPLE: User: "Send heartbeat for device P_abc123" device_heartbeat({ fingerprint: "P_abc123", status: "playing", current_ad_id: "507f1f77bcf86cd799439011", uptime_seconds: 3600 }). It is categorised as a Write tool in the Trillboards DOOH Advertising MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Trillboards DOOH Advertising MCP server in PolicyLayer and add a rule for device_heartbeat: 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 Trillboards DOOH Advertising. Nothing to install.
device_heartbeat 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 device_heartbeat 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 device_heartbeat. 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.
device_heartbeat is provided by the Trillboards DOOH Advertising MCP server (https://api.trillboards.com/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 74 Trillboards DOOH Advertising tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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