Open a new Chrome browser session on the dev machine. Returns a session_id to use in subsequent browser_* calls. Sessions persist across tool calls — cookies, auth state, and current URL survive between steps. Pass proxy_url to egress through a chosen vantage (a proxy or peer the user is entitled...
AI agents use browser_open to create or update resources in Yaver — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Yaver environment.
| Parameter | Type | Required | Description |
|---|---|---|---|
record | boolean | — | Record this session to an MP4 video of everything the agent does in it (headless-safe). The response returns clip_id + clip_url; the clip finalizes on browser_c |
headful | boolean | — | Show browser window visibly (default: false, headless) |
profile | string | — | F2 persistent profile (name or absolute path). Reuses a user-data-dir so cookies + Cloudflare clearance PERSIST across runs. Pass the SAME profile name to brows |
proxy_url | string | — | Egress proxy for this session's vantage, e.g. http://host:8080 or socks5://host:1080. Omit for machine-native egress. Only use proxies/peers the user owns or is |
session_id | string | — | Custom session ID (auto-generated if omitted) |
record_seconds | number | — | Optional safety cap (seconds) for recording; defaults to a 600s cap. Recording normally stops at browser_close, not this cap. |
Parameters from the server's own tool schema.
An AI agent can call browser_open faster than any human can review — one bad instruction and it creates or modifies resources in Yaver by the hundred, each call as confident as the last.
Attacks that exploit this kind of access
Open a new Chrome browser session on the dev machine. Returns a session_id to use in subsequent browser_* calls. Sessions persist across tool calls — cookies, auth state, and current URL survive between steps. Pass proxy_url to egress through a chosen vantage (a proxy or peer the user is entitled to use); the source then sees that egress IP, not this machine's. It is categorised as a Write tool in the Yaver MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
browser_open accepts 6 parameters: record, headful, profile, proxy_url, session_id, record_seconds. The full parameter table on this page comes from the server's own tool schema.
Register the Yaver MCP server in PolicyLayer and add a rule for browser_open: 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 Yaver. Nothing to install.
browser_open is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the browser_open 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.
Set action: deny in the PolicyLayer policy for browser_open. 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.
browser_open is provided by the Yaver MCP server (yaver-cli). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.