List all function and class definitions in a JavaScript file, with their start and end line numbers. Use this to get an overview of a JS file
AI agents call list_js_functions to retrieve information from FilesystemMCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves and displays metadata about JavaScript file structure (function/class names and line numbers) without any side effects. It does not execute code, modify files, delete content, or trigger external operations. It is a straightforward Read operation with minimal risk, appropriate for code analysis and navigation tasks.
From the tool's definition Tool description states it 'List all function and class definitions' and 'get an overview' — purely informational operations with no modification or execution.
Attacks that exploit this kind of access
List all function and class definitions in a JavaScript file, with their start and end line numbers. Use this to get an overview of a JS file. It is categorised as a Read tool in the FilesystemMCP MCP Server, which means it retrieves data without modifying state.
Register the Filesystem MCP server in PolicyLayer and add a rule for list_js_functions: 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 FilesystemMCP. Nothing to install.
list_js_functions 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_js_functions 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_js_functions. 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_js_functions is provided by the Filesystem MCP server (rijadalisic/filesystemmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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