browser.set_cookies · MCP Playwright Browser MCP

WHAT IT DOES

What browser.set_cookies does on MCP Playwright Browser

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

WHY IT NEEDS A POLICY

Why browser.set_cookies needs a policy

This tool modifies browser cookies, which are reversible session/authentication data. It creates or updates cookies without deleting them permanently, placing it in the Write category rather than Destructive.

From the tool's definition Tool name is 'browser.set_cookies' and description states 'Set cookies in the current browser context.' The verb 'set' indicates modification of browser state.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

browser.set_cookies Rate-limited

browser.set_cookies 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": {
    "browser.set_cookies": {
      "limits": [
        {
          "counter": "browser.set_cookies_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 MCP Playwright Browser, so you can run agents against it safely.

FAQ

Questions about browser.set_cookies

What does the browser.set_cookies tool do? +

Set cookies in the current browser context. It is categorised as a Write tool in the MCP Playwright Browser MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on browser.set_cookies? +

Register the MCP Playwright Browser MCP server in PolicyLayer and add a rule for browser.set_cookies: 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 MCP Playwright Browser. Nothing to install.

What risk level is browser.set_cookies? +

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

Can I rate-limit browser.set_cookies? +

Yes. Add a rate_limit block to the browser.set_cookies 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 browser.set_cookies completely? +

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

browser.set_cookies is provided by the MCP Playwright Browser MCP server (mhrnqaruni/mcp-playwright-browser). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.