apply_swap · Arvo MCP Server MCP: Risk & Policy

WHAT IT DOES

What apply_swap does on Arvo MCP Server

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

WHY IT NEEDS A POLICY

Why apply_swap needs a policy

The tool modifies workout configuration by applying an exercise swap. This is a Write action because it creates or modifies data reversibly (the swap can be undone or adjusted). It is not Execute because it does not run arbitrary code or trigger external operations with argument-dependent effects; it applies a pre-suggested swap within a constrained fitness domain.

From the tool's definition Tool description states 'Apply a previously suggested exercise swap to the workout' — this modifies workout data by swapping exercises, which is a reversible change to the user's training plan.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

apply_swap Rate-limited

apply_swap 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": {
    "apply_swap": {
      "limits": [
        {
          "counter": "apply_swap_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 Arvo MCP Server, so you can run agents against it safely.

FAQ

Questions about apply_swap

What does the apply_swap tool do? +

Apply a previously suggested exercise swap to the workout. It is categorised as a Write tool in the Arvo 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 apply_swap? +

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

What risk level is apply_swap? +

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

Can I rate-limit apply_swap? +

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

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

apply_swap is provided by the Arvo MCP Server MCP server (khaoss85/arvo-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.