npm_compare_packages

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

With no annotations, the description carries the full burden of behavioral disclosure. It adequately describes the core action and data points, but does not mention whether it is read-only, any potential network latency, or what the output format looks like. It is not misleading, but lacks the extra context that annotations would provide.

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 a single, dense sentence that front-loads the primary verb and resource, and then adds specific metrics. Every phrase earns its place; there is no fluff or redundancy.

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?

Given the simple single-parameter schema and no output schema, the description sufficiently lists all comparison dimensions and implies the need for 2+ packages. It does not explicitly mention output format or alternatives to sibling tools, but for a tool this straightforward, it is largely complete.

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 already provides a complete description for the 'packages' parameter, including type and min/max constraints. The tool description merely reinforces the comparison context without adding new parameter-level information. With high schema coverage, the baseline of 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 uses a specific verb ('Compare') and identifies the exact resource (npm packages), then enumerates the comparison dimensions (weekly downloads, bundle size, dependency count, last update, GitHub stars, license). This clearly distinguishes it from sibling tools like npm_search or npm_package_info, which focus on individual package lookup or search.

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 clearly implies a side-by-side comparison use case for multiple packages, which sets it apart from single-package tools. However, it does not explicitly state when not to use it (e.g., for a single package) or name alternatives like npm_package_info. Clear context with no exclusions earns a 4.

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