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

Annotations already declare readOnly, idempotent, and non-destructive behavior; the description adds substantial execution context: it fans out to external APIs, returns a specific summary block, and degrades gracefully when bundlephobia times out (5-30s first measurement, sources_failed field). No contradiction with annotations.

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 long but every sentence is information-dense: composite behavior, invocation triggers, return fields, ecosystem scope, and failure semantics. It is front-loaded with the core purpose before diving into details, and no sentence is filler.

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?

With no output schema, the description carries the full burden of explaining return values and does so by enumerating the summary block fields and listing additional outputs (per-advisory details, links, recent alternative versions). It also covers edge cases such as timeouts and non-NPM ecosystems, making the tool's behavior fully understood.

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%, so the baseline is 3. The description goes slightly beyond by adding the ecosystem constraint 'NPM ecosystem only in v1' and clarifying that version defaults to latest via 'is_latest' context. Most parameter semantics still reside in the schema, but this added constraint earns a 4.

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 verb+resource: 'Composite ... check in ONE call' and explicitly names the data sources (deps.dev, bundlephobia). It states the user-facing purpose ('should I add this npm package to my project') in plain terms, making it unambiguous what the tool does and how it differs from generic research tools.

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 says 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'—direct when-to-use guidance. It also names the alternative for non-NPM ecosystems ('PyPI / Maven / Cargo / Go fall under deps.dev:version directly'), giving clear boundary conditions.

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