set_pre_call_api · Smallest MCP: Risk & Policy

WHAT IT DOES

What set_pre_call_api does on Smallest

AI agents use set_pre_call_api to create or update resources in Smallest — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Smallest environment.

WHY IT NEEDS A POLICY

Why set_pre_call_api needs a policy

This tool modifies agent configuration, which is a Write operation — it creates or updates settings reversibly. While configuration changes can have significant operational impact (hence 'high' severity due to potential for disruption if misconfigured), they are not Financial, Destructive, or Execute operations.

From the tool's definition Tool name 'set_pre_call_api' and description 'Configure (or disable) an agent' indicate modification of agent configuration settings. The ability to configure or disable an agent constitutes reversible changes to agent state and behavior.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_pre_call_api Rate-limited

set_pre_call_api 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.

View as policy code

policy.json

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

LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Smallest, so you can run agents against it safely.

FAQ

Questions about set_pre_call_api

What does the set_pre_call_api tool do? +

Configure (or disable) an agent. It is categorised as a Write tool in the Smallest 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_pre_call_api? +

Register the Smallest MCP server in PolicyLayer and add a rule for set_pre_call_api: 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 Smallest. Nothing to install.

What risk level is set_pre_call_api? +

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

Can I rate-limit set_pre_call_api? +

Yes. Add a rate_limit block to the set_pre_call_api 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_pre_call_api completely? +

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

set_pre_call_api is provided by the Smallest MCP server (@developer-smallestai/smallest-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.