validate_email

THE RISK

Low Risk

Why validate_email needs a policy

validate_email is a pure validation/checking function that queries and evaluates data format without side effects. It does not write, delete, execute commands, or move funds. This is a classic Read operation: it inspects input and returns a result based on analysis.

From the tool's definition Tool description states it 'Checks a simple email format' and 'Returns isError when invalid' — a validation operation that performs format checking without modifying, creating, deleting, or executing external operations.

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

POLICY

How to control validate_email

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "validate_email": {}
  }
}

validate_email is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.

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

CAP THIS TOOL →

Free to start. No card required.

EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Data exfiltration → How read access becomes an exfiltration channel when chained with untrusted content.
MCP token cost → What connecting this server costs in context-window tokens on every request.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about validate_email

What does the validate_email tool do? +

Checks a simple email format. Returns isError when invalid. It is categorised as a Read tool in the MCP from Scratch Server MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on validate_email? +

Register the MCP from Scratch Server MCP server in PolicyLayer and add a rule for validate_email: 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 MCP from Scratch Server. Nothing to install.

What risk level is validate_email? +

validate_email is a Read tool with low risk. Read-only tools are generally safe to allow by default.

Can I rate-limit validate_email? +

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

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

validate_email is provided by the MCP from Scratch Server MCP server (pguso/mcp-from-scratch). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every MCP from Scratch Server tool call.

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

CHECK YOUR STACK →