json_strlen

THE RISK

Low Risk

Why json_strlen needs a policy

This tool retrieves metadata (string length) about JSON data at a specified path. It performs a non-destructive read operation with no side effects, no state modification, and no capability to execute external operations or delete data. The minimal scope and read-only nature warrant a 'low' severity classification.

From the tool's definition Tool name is 'json_strlen' with description 'Get the length of string at path.' The verb 'Get' indicates a retrieval operation that queries or inspects data without modifying it.

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

POLICY

How to control json_strlen

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

policy.json

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

json_strlen 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 Awslabs Amazon Sns Sqs — 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

Roll out MCP under one policy → Per-person scoped tokens, one central policy, and full audit across every server your team connects.
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 →
PolicyLayer vs alternatives → How deterministic, per-call MCP policy compares with gateways, identity layers, and authorisation platforms.

FAQ

Questions about json_strlen

What does the json_strlen tool do? +

Get the length of string at path. It is categorised as a Read tool in the Awslabs Amazon Sns Sqs MCP Server, which means it retrieves data without modifying state.

How do I enforce a policy on json_strlen? +

Register the Awslabs Amazon Sns Sqs MCP server in PolicyLayer and add a rule for json_strlen: 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 Awslabs Amazon Sns Sqs. Nothing to install.

What risk level is json_strlen? +

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

Can I rate-limit json_strlen? +

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

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

json_strlen is provided by the Awslabs Amazon Sns Sqs MCP server (awslabs.amazon-sns-sqs-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Awslabs Amazon Sns Sqs tool call.

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

CHECK YOUR STACK →