sessions_update · CyPerf MCP Server MCP: Risk & Policy

WHAT IT DOES

What sessions_update does on CyPerf MCP Server

AI agents use sessions_update to create or update resources in CyPerf MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your CyPerf MCP Server environment.

WHY IT NEEDS A POLICY

Why sessions_update needs a policy

This tool creates or modifies session properties without permanently deleting or irreversibly destroying data, placing it in the Write category. The 'update' operation is reversible—properties can be modified again or reverted.

From the tool's definition 'Update session properties' indicates the tool modifies existing session configuration data. The term 'update' is a reversible write operation that changes session state or settings.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

sessions_update Rate-limited

sessions_update 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "sessions_update": {
      "limits": [
        {
          "counter": "sessions_update_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches CyPerf MCP Server, so you can run agents against it safely.

FAQ

Questions about sessions_update

What does the sessions_update tool do? +

[Sessions] Update session properties. It is categorised as a Write tool in the CyPerf MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on sessions_update? +

Register the CyPerf MCP Server MCP server in PolicyLayer and add a rule for sessions_update: 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 CyPerf MCP Server. Nothing to install.

What risk level is sessions_update? +

sessions_update is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit sessions_update? +

Yes. Add a rate_limit block to the sessions_update 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.

How do I block sessions_update completely? +

Set action: deny in the PolicyLayer policy for sessions_update. 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.

What MCP server provides sessions_update? +

sessions_update is provided by the CyPerf MCP Server MCP server (keysight/cyperf-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.