browser_localstorage_set

A write tool on the Playwright MCP server.

SERVERPlaywright SOURCEhanato238/playwright-mcp

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/hanato238-playwright-mcp/browser-localstorage-set.md

WHAT IT DOES

What browser_localstorage_set does on Playwright

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

RISK

Why browser_localstorage_set is rated Medium

Setting local storage values modifies client-side persistent data reversibly. This is a Write operation—data can be updated or cleared later. Severity is medium because an agent could abuse this to inject malicious data, tamper with application state, or degrade functionality, but the impact is typically scoped to a single browser context and session-dependent.

From the tool's definition Tool name 'browser_localstorage_set' indicates it sets values in browser local storage. The sibling context (browser_cookie_set, browser_cookie_get, etc.) confirms this is a browser state modification tool. Empty description lowers precision slightly.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs browser_localstorage_set safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Playwright, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For browser_localstorage_set, this is the rule to start with:

browser_localstorage_set Rate-limited

browser_localstorage_set 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_localstorage_set": {
      "limits": [
        {
          "counter": "browser_localstorage_set_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Playwright, apply this rule, and every browser_localstorage_set call is checked against it from then on.

FAQ

Questions about browser_localstorage_set

What does the browser_localstorage_set tool do? +

browser_localstorage_set is a write tool on the Playwright MCP server. It is categorised as a Write tool in the Playwright 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_localstorage_set? +

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

What risk level is browser_localstorage_set? +

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

Can I rate-limit browser_localstorage_set? +

Yes. Add a rate_limit block to the browser_localstorage_set 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_localstorage_set completely? +

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

browser_localstorage_set is provided by the Playwright MCP server (hanato238/playwright-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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