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GongRzhe

Terminal Controller for MCP

by GongRzhe

list_directory

List the files and subdirectories in any directory to inspect its contents.

Instructions

List files and subdirectories in the specified directory

Args:
    path: Directory path to list contents, default is current directory

Returns:
    List of directory contents

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
pathNo

Implementation Reference

  • The `list_directory` tool handler function, decorated with @mcp.tool(). Lists files and subdirectories in a given path (or current directory), returning a formatted string with 📁 for dirs and 📄 for files, sorted alphabetically.
    @mcp.tool()
    async def list_directory(path: Optional[str] = None) -> str:
        """
        List files and subdirectories in the specified directory
        
        Args:
            path: Directory path to list contents, default is current directory
        
        Returns:
            List of directory contents
        """
        if path is None:
            path = os.getcwd()
        
        try:
            items = os.listdir(path)
            
            dirs = []
            files = []
            
            for item in items:
                full_path = os.path.join(path, item)
                if os.path.isdir(full_path):
                    dirs.append(f"📁 {item}/")
                else:
                    files.append(f"📄 {item}")
            
            # Sort directories and files
            dirs.sort()
            files.sort()
            
            if not dirs and not files:
                return f"Directory '{path}' is empty"
            
            output = f"Contents of directory '{path}':\n\n"
            
            if dirs:
                output += "Directories:\n"
                output += "\n".join(dirs) + "\n\n"
            
            if files:
                output += "Files:\n"
                output += "\n".join(files)
            
            return output
        
        except FileNotFoundError:
            return f"Error: Directory '{path}' does not exist"
        except PermissionError:
            return f"Error: No permission to access directory '{path}'"
        except Exception as e:
            return f"Error listing directory contents: {str(e)}"
  • The registration is via the `@mcp.tool()` decorator on line 201, which registers `list_directory` as an MCP tool on the FastMCP server instance named 'mcp' (initialized on line 11).
    @mcp.tool()

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A3.7/5.0
Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are present, and the description only states the basic operation. It does not disclose behaviors such as whether hidden files are listed, how errors (e.g., invalid path) are handled, or if it follows symlinks. For a simple tool, this is adequate but not thorough.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise and front-loaded, with a clear statement of purpose followed by parameter details. Every sentence is informative, though the Args/Returns format is somewhat verbose for such a simple tool.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's simplicity and the lack of output schema, the description adequately covers the input and output. It explains the single parameter and the return value (list of contents), which is sufficient for an agent to use the tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

The description adds meaning to the 'path' parameter by explaining its purpose and default value, which is not fully conveyed by the schema alone (which only specifies type and nullability). Schema coverage is 0%, so the description compensates well.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the verb 'list' and the resource 'files and subdirectories' in a specified directory, which distinguishes it from sibling tools like read_file or write_file.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No guidance is provided on when to use this tool versus alternatives like change_directory or read_file. It does not mention when not to use it or any prerequisites.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.