Look up a hostname or IP address in the URLhaus database to find associated malware URLs. Returns all known malicious URLs hosted on that host.
Risk signalsAccepts URL/endpoint input (host)
Part of the Urlhaus server.
Free to start. No card required.
AI agents call lookup_host to retrieve information from Urlhaus 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 lookup_host 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": {
"lookup_host": {}
}
}See the full Urlhaus policy for all 24 tools.
These attack patterns abuse exactly the kind of access lookup_host 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.
Look up a hostname or IP address in the URLhaus database to find associated malware URLs. Returns all known malicious URLs hosted on that host.. It is categorised as a Read tool in the Urlhaus MCP Server, which means it retrieves data without modifying state.
Register the Urlhaus MCP server in PolicyLayer and add a rule for lookup_host: 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 Urlhaus. Nothing to install.
lookup_host 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 lookup_host 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 lookup_host. 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.
lookup_host is provided by the Urlhaus MCP server (https://gateway.pipeworx.io/urlhaus/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 24 Urlhaus tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
4,600+ MCP servers and 31,000+ tools scanned and risk-classified.