AI agents call list_classes to retrieve information from Pharo Smalltalk Interop without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves metadata about classes in the Pharo environment. Listing classes is a read-only operation with no side effects—it queries existing definitions without modifying or executing anything. Even if an agent calls this repeatedly, it cannot cause harm. Confidence is high despite empty description because the name and context are unambiguous.
From the tool's definition Tool name 'list_classes' indicates querying/listing class definitions in a Pharo Smalltalk image; no description provided but context from sibling tools (get_class_comment, get_class_source, get_method_source) suggests introspection/retrieval operations.
Documented attack patterns abuse exactly the kind of access list_classes gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Pharo Smalltalk Interop, and nothing reaches the server without passing your rules. This is the rule we recommend for list_classes:
{
"version": "1",
"default": "deny",
"tools": {
"list_classes": {}
}
}list_classes is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
Free to start. No card required.
list_classes. It is categorised as a Read tool in the Pharo Smalltalk Interop MCP Server, which means it retrieves data without modifying state.
Register the Pharo Smalltalk Interop MCP server in PolicyLayer and add a rule for list_classes: 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 Pharo Smalltalk Interop. Nothing to install.
list_classes 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_classes 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_classes. 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_classes is provided by the Pharo Smalltalk Interop MCP server (mumez/pharo-smalltalk-interop-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Pharo Smalltalk Interop, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
Free to start. No card required.
23 Pharo Smalltalk Interop tools catalogued and risk-classified — across an index of 43,000+ MCP servers.