set-api-url

THE RISK

Medium Risk

Why set-api-url needs a policy

This tool modifies API endpoint configuration, which is a reversible write operation affecting how all subsequent requests are routed. While not directly creating or deleting data, it changes system configuration that could redirect requests to unintended servers if misconfigured by an agent.

From the tool's definition Tool name 'set-api-url' and description 'Set the API base URL for all requests' indicate modification of configuration state that persists across subsequent API calls.

Documented attack patterns abuse exactly the kind of access set-api-url gives an agent:

POLICY

How to control set-api-url

PolicyLayer is an MCP gateway — it sits between your AI agents and PI API MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for set-api-url:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "set-api-url": {
      "limits": [
        {
          "counter": "set-api-url_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

set-api-url 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 PI API 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

Related tools and policies

More PI API MCP Server tools

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All 18 PI API 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 set-api-url

What does the set-api-url tool do? +

Set the API base URL for all requests. It is categorised as a Write tool in the PI API 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 set-api-url? +

Register the PI API MCP Server MCP server in PolicyLayer and add a rule for set-api-url: 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 PI API MCP Server. Nothing to install.

What risk level is set-api-url? +

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

Can I rate-limit set-api-url? +

Yes. Add a rate_limit block to the set-api-url 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 set-api-url completely? +

Set action: deny in the PolicyLayer policy for set-api-url. 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 set-api-url? +

set-api-url is provided by the PI API MCP Server MCP server (mingzilla/pi-api-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 PI API MCP Server tool call.

Start from PI API 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 →