Watch an element for changes over time — use this INSTEAD of writing MutationObserver/setInterval/setTimeout code in evaluate. Two modes: (1) collect — watch for 'duration' ms, return all text/attribute changes (e.g. collect 3 values that appear one after another). (2) until — wait for a conditio...
Part of the Chrome server.
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AI agents call observe to retrieve information from Chrome without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though observe only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"observe": {}
}
}See the full Chrome policy for all 23 tools.
These attack patterns abuse exactly the kind of access observe gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Watch an element for changes over time — use this INSTEAD of writing MutationObserver/setInterval/setTimeout code in evaluate. Two modes: (1) collect — watch for 'duration' ms, return all text/attribute changes (e.g. collect 3 values that appear one after another). (2) until — wait for a condition, then optionally click immediately (e.g. click Capture when counter hits 8). Use click_first to trigger the action that causes changes (observer is set up BEFORE the click, so nothing is missed).. It is categorised as a Read tool in the Chrome MCP Server, which means it retrieves data without modifying state.
Register the Chrome MCP server in PolicyLayer and add a rule for observe: 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 Chrome. Nothing to install.
observe 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 observe 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 observe. 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.
observe is provided by the Chrome MCP server (@silbercue/chrome). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 23 Chrome tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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