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

Beyond the read-only and idempotent annotations, the description discloses behavior such as fanning out across two services, partial failure degradation, and the 5-30s latency for bundlephobia's first measurement. It also explains the 'sources_failed' output when timeouts occur. This adds significant behavioral context that annotations alone do not 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 dense but every sentence serves a purpose: purpose, use cases, output summary, ecosystem scope, and failure handling are clearly delineated. It front-loads the primary function and avoids fluff. Despite its length, it remains well-structured and scannable.

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 composite tool with no output schema, the description fully accounts for complexity: it lists the exact output fields, describes per-advisory detail and links, explains ecosystem limitations, and covers failure modes with graceful degradation. This is complete enough for an agent to confidently invoke the tool and interpret results.

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 input schema already provides complete descriptions for both parameters (package name and version). The main description adds only a brief mention of scoped packages and default-to-latest behavior, which is already implied by the schema. Since schema coverage is 100%, the description adds minimal extra value for parameter semantics, aligning with the baseline of 3.

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 specific verb and resource: "Composite 'should I add this npm package to my project' check in ONE call." It clearly distinguishes the tool from siblings by naming the external data sources (deps.dev, bundlephobia) and the exact question it answers. This makes its purpose unambiguous and unique among the listed sibling 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 states when to use the tool: "Use whenever an agent asks 'is X safe / popular / small' or 'what does adding lodash cost me'." It also gives an exclusion criterion for non-NPM ecosystems, directing users to "deps.dev:version directly" for PyPI/Maven/Cargo/Go. This provides clear context and a fallback alternative.

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