Assert that the number of elements matching the selector equals expected count
AI agents call assert_count to retrieve information from MCP Playwright Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a read/verification operation — it checks/counts DOM elements matching a selector and compares to an expected value. It has no side effects on the browser state, data, or external systems. It only reads and validates, similar to the other assert_* tools in this server.
From the tool's definition Assert that the number of elements matching the selector equals expected count
Attacks that exploit this kind of access
Assert that the number of elements matching the selector equals expected count. It is categorised as a Read tool in the MCP Playwright Server MCP Server, which means it retrieves data without modifying state.
Register the MCP Playwright Server MCP server in PolicyLayer and add a rule for assert_count: 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 Server. Nothing to install.
assert_count 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 assert_count 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 assert_count. 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.
assert_count is provided by the MCP Playwright Server MCP server (j0hanz/playwright-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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