AI agents call check_connection to retrieve information from Joern MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a simple connectivity verification to confirm the Joern server is operational. It is a read-only diagnostic check that queries the status of the MCP plugin without side effects, data modification, or code execution. It poses minimal security risk as it only returns operational status information.
From the tool's definition Tool name 'check_connection' and description 'Check if the Joern MCP plugin is running' indicate a diagnostic status check operation with no data retrieval, modification, or execution capabilities.
Documented attack patterns abuse exactly the kind of access check_connection gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Joern MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for check_connection:
{
"version": "1",
"default": "deny",
"tools": {
"check_connection": {}
}
}check_connection is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Check if the Joern MCP plugin is running. It is categorised as a Read tool in the Joern MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Joern MCP Server MCP server in PolicyLayer and add a rule for check_connection: 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 Joern MCP Server. Nothing to install.
check_connection 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 check_connection 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 check_connection. 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.
check_connection is provided by the Joern MCP Server MCP server (sfncat/mcp-joern). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 21 Joern MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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21 Joern MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.