AI agents call search_user to retrieve information from HackerNews MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves public HackerNews user profile data without creating, modifying, deleting, executing code, or initiating financial transactions. It is a straightforward read operation querying existing data from HackerNews, typical of publicly available user lookup functionality. The blast radius of misuse is minimal as it only exposes public user information already accessible through the HackerNews website.
From the tool's definition Tool name 'search_user' and description 'Get a HackerNews user' indicate retrieval of user information with no modification or side effects.
Documented attack patterns abuse exactly the kind of access search_user gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and HackerNews MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for search_user:
{
"version": "1",
"default": "deny",
"tools": {
"search_user": {}
}
}search_user is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Get a HackerNews user. It is categorised as a Read tool in the HackerNews MCP Server MCP Server, which means it retrieves data without modifying state.
Register the HackerNews MCP Server MCP server in PolicyLayer and add a rule for search_user: 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 HackerNews MCP Server. Nothing to install.
search_user 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 search_user 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 search_user. 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.
search_user is provided by the HackerNews MCP Server MCP server (traves-theberge/hackernews-mcp-typescript). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from HackerNews MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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6 HackerNews MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.