Sets a breakpoint that triggers when an XHR/Fetch request URL contains the specified string.
AI agents invoke break_on_xhr to trigger actions in JS Reverse Strong MCP. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.
Setting a breakpoint is a debugging/execution control operation that affects the runtime behavior of the browser environment. It hooks into the JavaScript execution engine to pause execution when a condition is met, which is an active intervention in a running process rather than a passive read. This falls under Execute as it triggers external operations in the browser runtime.
From the tool's definition Sets a breakpoint that triggers when an XHR/Fetch request URL contains the specified string
Documented attack patterns abuse exactly the kind of access break_on_xhr gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and JS Reverse Strong MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for break_on_xhr:
{
"version": "1",
"default": "deny",
"tools": {
"break_on_xhr": {
"limits": [
{
"counter": "break_on_xhr_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}break_on_xhr stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.
Free to start. No card required.
Sets a breakpoint that triggers when an XHR/Fetch request URL contains the specified string. It is categorised as a Execute tool in the JS Reverse Strong MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the JS Reverse Strong MCP server in PolicyLayer and add a rule for break_on_xhr: 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 JS Reverse Strong MCP. Nothing to install.
break_on_xhr 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 break_on_xhr 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 break_on_xhr. 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.
break_on_xhr is provided by the JS Reverse Strong MCP server (lwjjike/jsreverser-strong-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from JS Reverse Strong MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
85 JS Reverse Strong MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.