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

Annotations mark it read-only, idempotent, and non-destructive, and the description adds substantial behavioral detail beyond that: it fans out to multiple services, handles partial failures gracefully, notes that bundlephobia's first measurement can take 5-30s, and explains that sources_failed will report timeouts. No contradictions.

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 well-structured: it opens with a clear one-line summary, then details data sources, usage triggers, return contents, limitations, and failure behavior. Every sentence adds value, though it is somewhat long; the length is justified by 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?

No output schema exists, so the description carries the full burden of explaining return values. It lists the summary block fields (is_latest, license, etc.), mentions per-advisory detail, links, and alternative versions. It also covers ecosystem scope and partial failure behavior, making it complete for a composite tool.

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%, so parameters are well-documented in the schema. The description adds a little context (e.g., default behavior for version, ecosystem scope) but does not substantially extend the schema's param descriptions. Baseline 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 a specific purpose: a composite 'should I add this npm package' check that fans out across deps.dev and bundlephobia. It identifies the resource (npm package), the verb (scan), and differentiates from siblings by specifying the ecosystem and the data sources.

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?

Explicitly tells when to use the tool ('use whenever an agent asks is X safe / popular / small') and provides an exclusion: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly.' This gives clear context and a pointer to an alternative approach.

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