Create a cyclic data subscription for an entity. Subscribes to periodic data updates. Required fields in sub_config:
AI agents use ros2_medkit_create_cyclic_sub to create or update resources in Ros2 Medkit — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Ros2 Medkit environment.
Creating a subscription is a reversible write operation that configures the system to track data streams. It modifies system state (adds a new subscription) but can be undone by removing the subscription. This is more severe than a Read operation (which merely retrieves data) but less severe than Destructive (which cannot be undone) or Execute/Financial operations.
From the tool's definition Tool name includes 'create' and description states 'Create a cyclic data subscription' — this creates a new subscription entity that modifies system state by establishing an ongoing data flow.
Documented attack patterns abuse exactly the kind of access ros2_medkit_create_cyclic_sub gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Ros2 Medkit, and nothing reaches the server without passing your rules. This is the rule we recommend for ros2_medkit_create_cyclic_sub:
{
"version": "1",
"default": "deny",
"tools": {
"ros2_medkit_create_cyclic_sub": {
"limits": [
{
"counter": "ros2_medkit_create_cyclic_sub_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}ros2_medkit_create_cyclic_sub 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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Create a cyclic data subscription for an entity. Subscribes to periodic data updates. Required fields in sub_config:. It is categorised as a Write tool in the Ros2 Medkit MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Ros2 Medkit MCP server in PolicyLayer and add a rule for ros2_medkit_create_cyclic_sub: 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 Ros2 Medkit. Nothing to install.
ros2_medkit_create_cyclic_sub 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 ros2_medkit_create_cyclic_sub 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 ros2_medkit_create_cyclic_sub. 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.
ros2_medkit_create_cyclic_sub is provided by the Ros2 Medkit MCP server (selfpatch/ros2_medkit_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Ros2 Medkit, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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84 Ros2 Medkit tools catalogued and risk-classified — across an index of 43,000+ MCP servers.