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

Beyond the annotations (readOnly, idempotent, non-destructive), the description discloses rich behavioral details: it fans out across two services, returns a specific summary block, and handles partial failures gracefully with a noted 5-30s latency for first bundlephobia measurement. It also mentions that sources_failed will list any timeout, ensuring the agent knows what to expect.

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 starts with the core purpose, then gives use-case triggers, enumerates the exact return fields, states the ecosystem constraint, and ends with error/failure handling. Every sentence earns its place without redundancy or 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?

With no output schema, the description compensates by explicitly listing all returned fields in the summary block, plus per-advisory details, links, and alternative versions. It also covers edge cases like partial failures and timeout behavior. This is a complete picture for an agent 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 fully documents both parameters with 100% coverage, including scoped package support and version defaulting. The description adds minimal extra parameter semantics, mostly reiterating what the schema says. The baseline of 3 applies because schema does the heavy lifting; the description doesn't need to compensate.

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 check for 'should I add this npm package' combining deps.dev and bundlephobia. It explicitly mentions the specific verb ('check'), resource ('npm package'), and lists the outputs (summary block, advisories, links, alternatives). It distinguishes itself from siblings by focusing on dependency risk/cost analysis.

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 explicit when-to-use guidance: whenever an agent asks 'is X safe / popular / small' or 'what does adding lodash cost me'. It also states the NPM-only limitation and directs users to deps.dev:version directly for PyPI/Maven/Cargo/Go packages. This clearly delineates usage vs alternatives.

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