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

The description adds substantial behavioral context beyond annotations: it explains the fan-out to two services, graceful degradation, potential 5-30s latency for first bundlephobia measurement, and the sources_failed field. It discloses NPM-only scope. No contradiction with the readOnly/idempotent annotations; the behavior is consistent with a read-only composite lookup.

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 contributes: purpose, usage trigger, return summary block, ecosystem scope, and failure behavior. It is front-loaded with the core purpose and remains information-rich without redundancy for the tool's complexity.

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 tool's high complexity and absence of an output schema, the description fully discloses the return format (summary fields, advisories, links, alternative versions), failure modes, and latency expectations. It also covers ecosystem limitations. No significant information gap remains for an agent to invoke or 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?

Schema coverage is 100% and already describes both parameters (package name with scoped-package acceptance, version default). The description adds meaning by tying parameters to the data sources and giving a concrete use-case example ('what does adding lodash cost me'), plus clarifying that version is optional in context. This is moderate added value over the schema, so a 4 is warranted.

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+resource: 'Composite "should I add this npm package to my project" check in ONE call'. It clearly identifies what the tool does (composite scan across deps.dev and bundlephobia) and differentiates it from simpler siblings like package_show or package_search by emphasizing the combined, one-call nature.

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?

Guidance is explicit: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me".' It also states when not to use (non-NPM ecosystems fall under deps.dev:version directly), providing clear exclusions and direction to alternatives.

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