Lists files in a directory, optionally filtering by extensions and recursing into subdirectories, so MCP clients can discover files for filesystem operations.
List files in a directory with optional extension filtering
| Name | Required | Description | Default |
|---|---|---|---|
| directory | No | Directory to list | . |
| recursive | No | Recurse into subdirectories | |
| extensions | No | Filter by extensions e.g. ['.pdf', '.txt'] | |
| max_results | No | Maximum results to return |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden of behavioral disclosure and falls short: it doesn't say what happens on a nonexistent directory, whether hidden files are included, what ordering is used, or whether results are truncated at max_results. Neither the default directory ('.') nor the recursive traversal caveat is surfaced in the description.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
A single front-loaded sentence with no filler. It is efficient, though the brevity is partly the source of the specification gaps noted elsewhere.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a 4-parameter tool with no annotations and no output schema, the description omits the return shape (paths vs. objects), behavior when max_results truncates, and error/edge-case handling. An agent could invoke it, but not predict its output or limits.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 100%, so directory, recursive, extensions, and max_results are already documented in the schema, including the extension-format example. The description adds no semantics beyond what the schema provides, so the baseline 3 applies.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description states a specific verb and resource ('List files in a directory') and adds the scoping qualifier 'with optional extension filtering'. It is clear on its own, but does not distinguish itself from siblings such as search_in_file or watch_directory, so an agent must infer the boundary.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
There is no guidance on when to use this tool versus search_in_file (content search), read_file, or watch_directory. No prerequisites, exclusions, or conditions are stated; usage is only implied by the name.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.