rpc_fill_signin_credentials · Rpcclient MCP: Risk & Policy

WHAT IT DOES

What rpc_fill_signin_credentials does on Rpcclient

AI agents invoke rpc_fill_signin_credentials to trigger actions in Rpcclient. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why rpc_fill_signin_credentials needs a policy

This tool actively performs sign-in actions by filling credentials into iOS apps or Safari overlays, triggering authentication flows. It executes external operations (UI interaction, credential submission) whose effects depend on the provided arguments. Misuse could result in unauthorized authentication or credential exposure, making severity high.

From the tool's definition Fill sign-in credentials with support for app-stage or Safari-overlay-stage password entry

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

rpc_fill_signin_credentials Rate-limited

rpc_fill_signin_credentials stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "rpc_fill_signin_credentials": {
      "limits": [
        {
          "counter": "rpc_fill_signin_credentials_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about rpc_fill_signin_credentials

What does the rpc_fill_signin_credentials tool do? +

Fill sign-in credentials with support for app-stage or Safari-overlay-stage password entry. It is categorised as a Execute tool in the Rpcclient MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on rpc_fill_signin_credentials? +

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

What risk level is rpc_fill_signin_credentials? +

rpc_fill_signin_credentials is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit rpc_fill_signin_credentials? +

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

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

rpc_fill_signin_credentials is provided by the Rpcclient MCP server (appknox/rpcclient-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.