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

Beyond annotations, the description discloses important behavioral traits: it fans out to external services, first measurement on a new version can take 5-30s, and partial failures degrade gracefully with sources_failed reporting. It also outlines the return structure. Annotations indicate read-only/idempotent, and the description aligns without contradiction.

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?

Although the description is long, it is dense with necessary operational details: purpose, trigger phrases, output fields, ecosystem scope, and failure handling. Every sentence earns its place, and it is efficiently structured with dashes and clauses rather than 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?

For a tool with no output schema, the description enumerates return fields in prose, covers latency and timeout behavior, and specifies ecosystem limitations. It gives an agent everything needed to select and invoke the tool correctly 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 fully describes both parameters (package name with scoped package handling, version with default-to-latest). The description adds no additional parameter-level semantics, so a baseline 3 is appropriate given 100% schema coverage.

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 composite check for npm packages, naming the exact sources (deps.dev, bundlephobia) and the question it answers ('should I add this npm package to my project'). It also clearly distinguishes from alternatives by declaring NPM-only in v1, which separates it from other ecosystem-specific 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?

Explicit usage guidance is provided: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also gives exclusion criteria for non-NPM ecosystems, directing agents to deps.dev:version instead, which is a clear when-not-to-use mandate.

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