AI agents call browser_extract_attribute to retrieve information from Yaver without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
| Parameter | Type | Required | Description |
|---|---|---|---|
selector | string | Yes | CSS selector |
attribute | string | Yes | Attribute name (e.g., href, value, data-id) |
session_id | string | Yes | Session ID |
Parameters from the server's own tool schema.
Even though browser_extract_attribute only reads data, uncontrolled read access leaks sensitive information and racks up API costs — an agent caught in a retry loop can make thousands of calls a minute without anyone noticing.
Attacks that exploit this kind of access
Extract an HTML attribute value from an element (e.g., href, src, value, data-*). It is categorised as a Read tool in the Yaver MCP Server, which means it retrieves data without modifying state.
browser_extract_attribute accepts 3 parameters: selector, attribute, session_id. Required: selector, attribute, session_id. 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_extract_attribute: 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_extract_attribute is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the browser_extract_attribute 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_extract_attribute. 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_extract_attribute 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.