open_path

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

With no annotations provided, the description carries the full transparency burden. It discloses the underlying mechanism ('Uses Windows Start-Process under the hood') and details what happens for each input type (registered app, Explorer, web browser). It does not discuss error behavior or whether the call blocks, but for a simple open operation, this is adequate.

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?

The description is concise and efficiently structured: an overview sentence, a breakdown by target type, and a use-case sentence. There is no fluff, and every sentence contributes meaningful information.

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 simple tool with one parameter, no output schema, and no annotations, the description covers the purpose, target types, use cases, and implementation detail. It is fully sufficient for an agent to understand when and how to invoke it.

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?

The schema describes the single parameter 'target' in detail with examples, so schema coverage is 100%. The description doesn't add new syntactic or format details for the parameter itself, but it does clarify behavior based on target type. Per the rubric, when schema coverage is high, a baseline of 3 is appropriate.

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 opens with a clear, specific verb+resource: 'Open a file, folder, or URL using the default application on this Windows PC.' It then breaks down behavior for each target type, which distinctly positions it against siblings like file_read (which reads content) and run_command (which executes commands).

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?

The description explicitly enumerates when to use the tool: 'Use this to open documents, launch applications via file shortcuts, browse folders in Explorer, or open websites in the browser.' It provides clear context but does not explicitly name alternatives or exclusionary conditions, so it misses the top score.

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