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

The description goes beyond the readOnlyHint and idempotentHint annotations by detailing fan-out behavior, partial failure degradation (bundlephobia timeouts with sources_failed), and latency expectations (5-30s for first measurement). This equips the agent with realistic behavioral context.

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 structured: it opens with the composite purpose, then usage, then return fields, then ecosystem scope and failure behavior. Every sentence adds value, but it is a bit long and could be tightened. It earns a 4 for being well-organized without 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?

Despite lacking an output schema, the description enumerates the return fields (is_latest, license, published_at, advisory_count, bundle_kb_min, bundle_kb_gz, dependency_count, has_esm, tree_shakeable), plus per-advisory detail, links, and alternatives. It also covers ecosystem limitations and error handling, making it highly 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?

The input schema already provides full descriptions for both parameters (package, version). The description adds contextual usage examples ('what does adding lodash cost me') and ecosystem constraints, but doesn't specify parameter-level syntax or format beyond the schema. Baseline 3 is appropriate given 100% schema coverage.

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 specifies what it measures (license, advisories, version history, bundle size, dependency count, ESM/tree-shake support) and distinguishes itself from siblings by being npm-specific.

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: 'Use whenever an agent asks is X safe / popular / small' or 'what does adding lodash cost me'. Also provides an exclusion and alternative: 'NPM ecosystem only in v1; PyPI / Maven / Cargo / Go fall under deps.dev:version directly.' This clearly states when to use and when not to.

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