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

Discloses important behavioral traits beyond annotations: composite fan-out across two services, partial failure degradation, 5-30s first measurement delay for bundlephobia, sources_failed reporting on timeout, and ecosystem limitation (NPM only in v1). Annotations already state readOnly/idempotent/non-destructive, and the description adds valuable operational context without contradicting them.

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?

Though longer than average, every sentence serves a purpose: defining scope, enumerating sources, listing output fields, giving usage triggers, noting ecosystem boundaries, and explaining failure behavior. The structure is logical and front-loaded with the core purpose, making it efficient for AI parsing.

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 complexity (composite, two sources, partial failure, latency) and absence of an output schema, the description fully compensates by listing the exact summary block fields (is_latest, license, published_at, advisory_count, bundle_kb_min, bundle_kb_gz, dependency_count, has_esm, tree_shakeable), per-advisory detail, links, alternative versions, and timeout behavior. Nothing critical is left undefined.

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%: both 'package' and 'version' have descriptions, including scoped package acceptance and default-to-latest behavior. The description does not add additional parameter semantics beyond what the schema already provides, so baseline 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 a composite check for npm packages using deps.dev and bundlephobia, with a specific verb ('scan') and resource ('npm package'). It explicitly positions itself as a one-call answer to 'should I add this package' and distinguishes it from the sibling tool scan_competitor_ai_presence by focusing on dependency safety/size rather than AI presence.

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?

Provides explicit when-to-use triggers: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also gives a clear exclusion: non-NPM ecosystems (PyPI, Maven, Cargo, Go) should go directly to deps.dev:version, which is an alternative tool usage.

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