update_plan · Tpc MCP: Risk & Policy

WHAT IT DOES

What update_plan does on Tpc

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

WHY IT NEEDS A POLICY

Why update_plan needs a policy

This tool modifies existing plan records. Update operations are categorized as Write because they create or modify data reversibly. The severity is medium rather than high because the blast radius depends on what plans control—if they govern critical system behavior or high-stakes decisions, severity could be higher, but without that context, medium reflects typical update operation risk.

From the tool's definition Tool name 'update_plan' and description 'Update an existing plan' indicate modification of existing data. The operation is reversible (can be updated again) and does not delete or destroy data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_plan Rate-limited

update_plan 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": {
    "update_plan": {
      "limits": [
        {
          "counter": "update_plan_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 Tpc, so you can run agents against it safely.

FAQ

Questions about update_plan

What does the update_plan tool do? +

Update an existing plan. It is categorised as a Write tool in the Tpc MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_plan? +

Register the Tpc MCP server in PolicyLayer and add a rule for update_plan: 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 Tpc. Nothing to install.

What risk level is update_plan? +

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

Can I rate-limit update_plan? +

Yes. Add a rate_limit block to the update_plan 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 update_plan completely? +

Set action: deny in the PolicyLayer policy for update_plan. 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 update_plan? +

update_plan is provided by the Tpc MCP server (suttonwilliamd/tpc-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.