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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds that results include both sizes and are framed for migration decisions, but says nothing about how 'similar' is ranked, result count limits, rate limits, or behaviour on an unknown package.

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 that front-loads the core action (return similar packages) before adding the size payload and the decision-support rationale. No filler and no 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?

An output schema exists, so the description needn't enumerate return fields — and it does describe the key content (packages plus minified+gzipped sizes anyway). Safety behaviour is covered by annotations. The remaining gap is the undocumented 'version' parameter and failure behaviour for unknown packages.

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 0% and there are 2 parameters, so the description must carry parameter meaning and largely does not. It refers obliquely to 'the given package' but never documents the package identifier format (scoped/namespaced names) or the optional 'version' parameter's semantics — whether it pins an exact version or defaults to latest.

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: return npm packages with similar functionality to a given package, plus their minified/gzipped sizes. It is clearly distinct from most siblings, though it never names the nearby 'size' or 'scan_dependency' tools that overlap on bundle-size/dependency data, so it stops short of full sibling differentiation.

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 closing clause 'to aid migration or replacement decisions' implies the usage context, which is more than nothing. However, there is no explicit when-to-use guidance, no mention of when to prefer 'size' or 'scan_dependency', and no conditions or prerequisites stated.

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