seed_auth_session · Custom Browser MCP: Risk & Policy

WHAT IT DOES

What seed_auth_session does on Custom Browser

AI agents invoke seed_auth_session to trigger actions in Custom Browser. 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 seed_auth_session needs a policy

The tool opens a headed (visible) Chromium browser tab, which constitutes triggering an external operation. The name 'seed_auth_session' suggests it also establishes or seeds an authentication session, which involves writing session/cookie state. Opening a browser tab with auth context could expose credentials or session tokens to misuse.

From the tool's definition 'opens a headed Chromium tab' — launches a browser process/tab, which is an external operation with side effects beyond simple data retrieval

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

seed_auth_session Rate-limited

seed_auth_session 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": {
    "seed_auth_session": {
      "limits": [
        {
          "counter": "seed_auth_session_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 Custom Browser, so you can run agents against it safely.

FAQ

Questions about seed_auth_session

What does the seed_auth_session tool do? +

v0.8.0: opens a headed Chromium tab on. It is categorised as a Execute tool in the Custom Browser MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on seed_auth_session? +

Register the Custom Browser MCP server in PolicyLayer and add a rule for seed_auth_session: 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 Custom Browser. Nothing to install.

What risk level is seed_auth_session? +

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

Can I rate-limit seed_auth_session? +

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

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

seed_auth_session is provided by the Custom Browser MCP server (theriz78/eclectique-browser-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.