AI agents call ucp_discover to retrieve information from Ucp without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
The tool name 'ucp_discover' strongly implies a read/search operation used to find UCP-enabled merchants, which aligns with the server description mentioning 'discovery' as one of its capabilities. Discovery tools are typically read-only with no side effects. However, the empty description lowers confidence, and severity is low since misuse of a discovery tool has minimal blast radius.
From the tool's definition Tool name 'ucp_discover' suggests discovery/search functionality; description is empty and uninformative.
Documented attack patterns abuse exactly the kind of access ucp_discover gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Ucp, and nothing reaches the server without passing your rules. This is the rule we recommend for ucp_discover:
{
"version": "1",
"default": "deny",
"tools": {
"ucp_discover": {}
}
}ucp_discover is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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ucp_discover. It is categorised as a Read tool in the Ucp MCP Server, which means it retrieves data without modifying state.
Register the Ucp MCP server in PolicyLayer and add a rule for ucp_discover: 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 Ucp. Nothing to install.
ucp_discover 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 ucp_discover 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 ucp_discover. 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.
ucp_discover is provided by the Ucp MCP server (nguthrie/ucp-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Ucp, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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5 Ucp tools catalogued and risk-classified — across an index of 43,000+ MCP servers.