[Feature Request] Support clientCertificates option for mTLS authentication

[karansachdeva001]

Summary

Add support for Playwright's native clientCertificates option to enable mutual TLS (mTLS) authentication with endpoints that require client certificates.

Use Case

Enterprise applications often require client certificate authentication for API endpoints. Native Playwright supports this via clientCertificates in browser context options, but MCP users cannot configure this.

Example - Native Playwright (works):

// playwright.config.ts
export default defineConfig({
  use: {
    clientCertificates: [{
      origin: 'https://secure-api.example.com',
      certPath: './certs/client.crt',
      keyPath: './certs/client.key',
    }],
    ignoreHTTPSErrors: true,
  },
});

MCP (not possible):
The playwright_navigate tool only accepts: url, browserType, headless, width, height, timeout, waitUntil. No certificate options exist.

Proposed Solution

Add certificate configuration to the MCP server, either via:

1. Tool parameter - Add clientCertificates array to navigation/context tools
2. Server configuration - Accept cert config at MCP server startup
3. Environment variables - Read cert paths from env vars

Option 1: Tool Parameter

// New parameter for playwright_navigate or a new tool
{
  url: "https://secure-api.example.com",
  clientCertificates: [{
    origin: "https://secure-api.example.com",
    certPath: "/path/to/client.crt",
    keyPath: "/path/to/client.key"
  }]
}

Option 2: Server Config (recommended)

// MCP server config
{
  "command": "npx",
  "args": ["-y", "@playwright/mcp"],
  "env": {
    "PLAYWRIGHT_CLIENT_CERT_ORIGIN": "https://secure-api.example.com",
    "PLAYWRIGHT_CLIENT_CERT_PATH": "/path/to/client.crt",
    "PLAYWRIGHT_CLIENT_KEY_PATH": "/path/to/client.key"
  }
}

Alternatives Considered

• Manual browser certificate selection: Doesn't work for automation
• Proxy with cert injection: Adds complexity and latency
• Using native Playwright tests: Works but loses MCP integration benefits

Additional Context

This would enable enterprise users to use MCP for authenticated browser automation, expanding the use cases significantly beyond public websites.

Related Playwright docs: https://playwright.dev/docs/api/class-testoptions#test-options-client-certificates