simulate_principal_policy

THE RISK

High Risk

Why simulate_principal_policy needs a policy

The tool name strongly suggests it simulates IAM principal policy evaluation (analogous to AWS IAM SimulatePrincipalPolicy API), which runs a simulation/execution of policy authorization checks against a principal. This is an Execute-category action as it triggers an evaluation/simulation engine.

From the tool's definition Tool name: 'simulate_principal_policy' — no description provided

Documented attack patterns abuse exactly the kind of access simulate_principal_policy gives an agent:

POLICY

How to control simulate_principal_policy

PolicyLayer is an MCP gateway — it sits between your AI agents and AWS, and nothing reaches the server without passing your rules. This is the rule we recommend for simulate_principal_policy:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "simulate_principal_policy": {
      "limits": [
        {
          "counter": "simulate_principal_policy_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

simulate_principal_policy stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

Create a free account and register AWS — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RATE-LIMIT THIS TOOL →

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EXPLORE

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Go deeper

Govern code and CI agents → Branch allowlists, approval on merges, and rate caps on the build and pipeline tools agents trigger.
High-risk tools in AWS → Every high-risk tool this server exposes, in one view.
All high-risk MCP tools → Every high-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Agent sandbox → Bounding what an agent can execute and where the boundary should sit.
Least privilege for MCP → Granting agents the minimum tool surface the task needs.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

FAQ

Questions about simulate_principal_policy

What does the simulate_principal_policy tool do? +

simulate_principal_policy. It is categorised as a Execute tool in the AWS MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on simulate_principal_policy? +

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

What risk level is simulate_principal_policy? +

simulate_principal_policy is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit simulate_principal_policy? +

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

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

simulate_principal_policy is provided by the AWS MCP server (@awslabs/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every AWS tool call.

Start from AWS, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

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