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

Beyond the readOnlyHint/openWorldHint annotations, the description discloses the on-demand external fetch for untracked names (consistent with openWorldHint) and three distinct result states: normal ranking, `pending` with a retry hint, and `notFound`. That state vocabulary is genuinely useful and not derivable from the annotations or schema.

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 sentence with no filler, and the core purpose (side-by-side comparison ranked by health) is front-loaded. It is dense with three semicolon-joined state clauses, which slightly taxes readability but every clause earns its place.

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 one-parameter read-only tool with no output schema, the description covers purpose, ranking behavior, and the key response states an agent must handle (`pending`, `notFound`). It omits any hint at the comparison payload's fields, but the state handling is the operationally important part.

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 coverage is 100% and already enforces the 2–5 count and npm name pattern, so the baseline would be 3. The description adds semantic value by explaining what happens to names passed in (untracked fetched on demand, in-progress scoring returns `pending`, unknown names return `notFound`), clarifying the accepted value domain.

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?

States a specific verb and resource ("Side-by-side comparison of 2–5 npm packages") plus the ordering rule ("ranked by health score"), which distinguishes it from a single-package inspect tool. However, it never names or contrasts itself with siblings like `audit`, `evaluate`, or `compat`, so the sibling-differentiation bar for a 5 is not met.

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 phrase "packages you are choosing between" implies the decision-support context, which is a reasonable usage cue. It gives no explicit when-not guidance and does not route the agent to alternatives such as `evaluate` for a single package or `compat` for interoperability checks.

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