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

The description richly discloses behavioral traits beyond annotations: it returns a summary block with specific fields, lists per-advisory detail and recent versions, and explicitly states that partial failures degrade gracefully with bundlephobia's first measurement potentially taking 5-30s and timing out being listed in sources_failed. This transparency exceeds what the readOnly/idempotent hints 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?

While the description is lengthy, every sentence earns its place: purpose, usage triggers, output details, ecosystem scope, and failure mode. It is well-structured with dashes and lists, and front-loaded with the core purpose. No fluff or 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?

The description is remarkably complete for a composite tool with no output schema. It explains return values (summary block, per-advisory detail, links, recent versions), data sources, ecosystem limitations, timeout behavior, and graceful degradation. There is no significant missing context.

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% with both parameters (package, version) fully described in the schema. The description does not add significant extra parameter semantics beyond what's in the schema, but it is consistent. Baseline 3 is appropriate since the schema carries the load.

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: a composite 'should I add this npm package' check that fans out across deps.dev and bundlephobia. It names specific resources and aspects (license, advisories, bundle size, tree-shaking), making it distinct from 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?

Explicit usage guidance is given: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also specifies ecosystem limitations (NPM only in v1, other ecosystems fall under deps.dev:version directly), providing clear direction on when this tool is appropriate versus alternatives.

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