string_set_range

THE RISK

Medium Risk

Why string_set_range needs a policy

The tool modifies string data by overwriting a portion of it. This is a Write operation (reversible modification), not Read (no retrieval), not Execute (no external commands), not Destructive (data can be recovered or the operation undone by overwriting again), and not Financial.

From the tool's definition Tool description states 'Overwrite part of string' — this is a modification operation that changes existing data.

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

POLICY

How to control string_set_range

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "string_set_range": {
      "limits": [
        {
          "counter": "string_set_range_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

string_set_range 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.

Create a free account and register Prometheus 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.

LIMIT THIS TOOL →

Free to start. No card required.

EXPLORE

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All 805 Prometheus MCP Server tools →

Write tools on other servers

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about string_set_range

What does the string_set_range tool do? +

Overwrite part of string. It is categorised as a Write tool in the Prometheus 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 string_set_range? +

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

What risk level is string_set_range? +

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

Can I rate-limit string_set_range? +

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

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

string_set_range is provided by the Prometheus MCP Server MCP server (awslabs.prometheus-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 Prometheus MCP Server tool call.

Start from Prometheus 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 →