auth_login · API MCP Server MCP: Risk & Policy

WHAT IT DOES

What auth_login does on API MCP Server

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

WHY IT NEEDS A POLICY

Why auth_login needs a policy

While auth_login primarily queries an API for authentication (which might seem like Read), the persistent side effect—storing a JWT locally—makes it a Write operation. Storing security tokens locally could enable subsequent unauthorized operations if misused by an agent.

From the tool's definition Tool modifies local state by 'storing' a JWT token for reuse. Authentication credentials are created/stored, which is a data modification operation, not merely reading data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

auth_login Rate-limited

auth_login 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": {
    "auth_login": {
      "limits": [
        {
          "counter": "auth_login_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 API MCP Server, so you can run agents against it safely.

FAQ

Questions about auth_login

What does the auth_login tool do? +

Authenticate against an API, extract a JWT, and store it locally for reuse. It is categorised as a Write tool in the 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 auth_login? +

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

What risk level is auth_login? +

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

Can I rate-limit auth_login? +

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

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

auth_login is provided by the API MCP Server MCP server (vilasone455/api-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.