AI agents call list-categories to retrieve information from PI API MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool queries and retrieves category data from the PI Dashboard without creating, modifying, or deleting any resources. It is a read-only operation that returns existing data, making it a 'Read' category risk with low severity since unauthorized access to category listings poses minimal harm compared to data modification or deletion.
From the tool's definition Tool name is 'list-categories' and description states 'List all categories with filtering support' — a retrieval operation with no modification of data.
Documented attack patterns abuse exactly the kind of access list-categories gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and PI API MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for list-categories:
{
"version": "1",
"default": "deny",
"tools": {
"list-categories": {}
}
}list-categories is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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List all categories with filtering support. It is categorised as a Read tool in the PI API MCP Server MCP Server, which means it retrieves data without modifying state.
Register the PI API MCP Server MCP server in PolicyLayer and add a rule for list-categories: 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 PI API MCP Server. Nothing to install.
list-categories 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 list-categories 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 list-categories. 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.
list-categories is provided by the PI API MCP Server MCP server (mingzilla/pi-api-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from PI API 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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18 PI API MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.