AI agents call list_categories to retrieve information from Graph Tool Call without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This is a straightforward read operation that returns information about available tool categories. It has no side effects, does not execute code or external operations, and does not modify or delete data. The blast radius of misuse is minimal—an agent could only learn what categories exist, which is non-sensitive graph structure information.
From the tool's definition Tool name 'list_categories' and description 'List all tool categories in the graph' indicate a retrieval operation that queries metadata about the tool graph without modifying, executing, or deleting anything.
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 Graph Tool Call, 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 tool categories in the graph. It is categorised as a Read tool in the Graph Tool Call MCP Server, which means it retrieves data without modifying state.
Register the Graph Tool Call 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 Graph Tool Call. 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 Graph Tool Call MCP server (sonaiengine/graph-tool-call). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Graph Tool Call, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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7 Graph Tool Call tools catalogued and risk-classified — across an index of 43,000+ MCP servers.