test_regex

THE RISK

High Risk

Why test_regex needs a policy

Running a regex engine against arbitrary input constitutes execution of a pattern-matching computation. While it has no persistent side effects, regex execution can be misused for ReDoS (Regular Expression Denial of Service) attacks by supplying catastrophically backtracking patterns, making it more than a simple read/query operation.

From the tool's definition Test regular expressions against text

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

POLICY

How to control test_regex

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

policy.json

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

test_regex 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 IT Tools MCP Server — 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 →

Free to start. No card required.

EXPLORE

Related tools and policies

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All 119 IT Tools MCP Server tools →

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Go deeper

High-risk tools in IT Tools MCP Server → 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 →

FAQ

Questions about test_regex

What does the test_regex tool do? +

Test regular expressions against text. It is categorised as a Execute tool in the IT Tools MCP Server MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on test_regex? +

Register the IT Tools MCP Server MCP server in PolicyLayer and add a rule for test_regex: 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 IT Tools MCP Server. Nothing to install.

What risk level is test_regex? +

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

Can I rate-limit test_regex? +

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

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

test_regex is provided by the IT Tools MCP Server MCP server (wrenchpilot/it-tools-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every IT Tools MCP Server tool call.

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

CHECK YOUR STACK →