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

Annotations already indicate read-only, idempotent, and non-destructive behavior, but the description adds valuable nuance: it explains partial failures degrade gracefully, that the first bundlephobia measurement can take 5-30 seconds, and that sources_failed will list timeouts. These details are not present in annotations and help the agent set expectations.

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 a tightly structured four-sentence paragraph that front-loads the purpose, then covers usage, output fields, and caveats. Each sentence earns its place, and the information is dense without fluff.

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 compensates by listing the exact summary block fields, mentioning per-advisory details, links, and alternative versions, and noting edge cases like bundlephobia timeouts and ecosystem scoping. This gives the agent enough context to use the tool correctly.

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 100% coverage for both parameters (package and version). The description confirms defaults and scoped package acceptance but does not add new semantic details beyond the schema, so the baseline score of 3 is appropriate.

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 clearly states the tool's purpose as a composite 'should I add this npm package to my project' check, naming the exact sources (deps.dev, bundlephobia) and the type of output. It also distinguishes from siblings by explicitly scoping to the NPM ecosystem in v1 and mentioning alternative routes for other ecosystems.

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 gives direct usage triggers: 'Use whenever an agent asks 'is X safe / popular / small' or 'what does adding lodash cost me''. It also explicitly directs non-NPM users to 'deps.dev:version directly', providing clear when-to-use versus alternative guidance.

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