AI agents call search_references 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 appears to search for or retrieve references to code elements (classes, methods, etc.) in a Smalltalk image. Search and query operations are Read category. Medium severity because even read operations on a live programming environment could expose sensitive code patterns, architecture details, or proprietary logic if misused by an agent.
From the tool's definition Tool name 'search_references' indicates a query/search operation with no side effects. No description provided, but naming convention suggests retrieval of reference information about code entities in the Pharo Smalltalk image.
Documented attack patterns abuse exactly the kind of access search_references 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 search_references:
{
"version": "1",
"default": "deny",
"tools": {
"search_references": {}
}
}search_references is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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search_references. 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 search_references: 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.
search_references 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_references 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_references. 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_references 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.
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23 Pharo Smalltalk Interop tools catalogued and risk-classified — across an index of 43,000+ MCP servers.