AI agents invoke run_qsreplace to trigger actions in Pentester-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.
qsreplace is typically used to automate injection of payloads into URL query parameters for testing web vulnerabilities. While this is a read-then-modify operation on URLs, the execution happens against external targets and the tool's primary function is to run a specialized command that manipulates and tests web endpoints—making it Execute rather than Write.
From the tool's definition Tool name 'run_qsreplace' is from the qsreplace penetration testing utility, which processes URLs to replace query string parameters with custom payloads—a reconnaissance and exploitation technique.
Documented attack patterns abuse exactly the kind of access run_qsreplace gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Pentester-MCP, and nothing reaches the server without passing your rules. This is the rule we recommend for run_qsreplace:
{
"version": "1",
"default": "deny",
"tools": {
"run_qsreplace": {
"limits": [
{
"counter": "run_qsreplace_rate",
"window": "minute",
"max": 10,
"scope": "grant"
}
]
}
}
}run_qsreplace 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.
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run_qsreplace. It is categorised as a Execute tool in the Pentester-MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Register the Pentester- MCP server in PolicyLayer and add a rule for run_qsreplace: 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 Pentester-MCP. Nothing to install.
run_qsreplace 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 run_qsreplace 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 run_qsreplace. 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.
run_qsreplace is provided by the Pentester- MCP server (halilkirazkaya/pentester-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Pentester-MCP, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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337 Pentester-MCP tools catalogued and risk-classified — across an index of 43,000+ MCP servers.