Run JavaScript in the browser page and return the result as text. Useful for extracting data, checking values, or triggering actions.
Accepts freeform code/query input (script)
Part of the Screenshotsmcp MCP server. Enforce policies on this tool with Intercept, the open-source MCP proxy.
AI agents invoke browser_evaluate to trigger processes or run actions in Screenshotsmcp. Execute operations can have side effects beyond the immediate call -- triggering builds, sending notifications, or starting workflows. Rate limits and argument validation are essential to prevent runaway execution.
browser_evaluate can trigger processes with real-world consequences. An uncontrolled agent might start dozens of builds, send mass notifications, or kick off expensive compute jobs. Intercept enforces rate limits and validates arguments to keep execution within safe bounds.
Execute tools trigger processes. Rate-limit and validate arguments to prevent unintended side effects.
tools:
browser_evaluate:
rules:
- action: allow
rate_limit:
max: 10
window: 60
validate:
required_args: trueSee the full Screenshotsmcp policy for all 56 tools.
Agents calling execute-class tools like browser_evaluate have been implicated in these attack patterns. Read the full case and prevention policy for each:
Other tools in the Execute risk category across the catalogue. The same policy patterns (rate-limit, validate) apply to each.
browser_evaluate is one of the high-risk operations in Screenshotsmcp. For the full severity-focused view — only the high-risk tools with their recommended policies — see the breakdown for this server, or browse all high-risk tools across every MCP server.
Run JavaScript in the browser page and return the result as text. Useful for extracting data, checking values, or triggering actions.. It is categorised as a Execute tool in the Screenshotsmcp MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Add a rule in your Intercept YAML policy under the tools section for browser_evaluate. You can allow, deny, rate-limit, or validate arguments. Then run Intercept as a proxy in front of the Screenshotsmcp MCP server.
browser_evaluate is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the browser_evaluate rule in your Intercept 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 Intercept policy for browser_evaluate. 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_evaluate is provided by the Screenshotsmcp MCP server (relievedattention992-smithery/screenshotsmcp). Intercept sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Open source. One binary. Zero dependencies.
npx -y @policylayer/intercept