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

Annotations already mark readOnly and idempotent, but the description adds critical behavior beyond that: partial failures degrade gracefully, bundlephobia's first measurement can take 5-30s, and sources_failed will list timeouts while the rest still returns. It also discloses the output structure including summary fields, per-advisory detail, links, and alternatives. This is rich, non-obvious 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 lengthy but every sentence earns its place. It is front-loaded with the core purpose, then use cases, then output summary, then ecosystem scope, then failure behavior. The structure is logical and skimmable despite its length.

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 of two external APIs) and the absence of an output schema, the description thoroughly explains what the tool returns (summary block with specific fields, per-advisory detail, links, and recent versions). It also covers ecosystem limitations, latency, and graceful degradation. This is complete for an agent to select and invoke 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 provides 100% coverage for both parameters, with detailed descriptions for 'package' (including scoped packages) and 'version' (including default behavior). The tool description adds no additional parameter semantics beyond what the schema states, so the 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 the verb 'scan' and the resource 'dependency', and explains it is a composite check across deps.dev and bundlephobia. It differentiates from siblings by explicitly limiting to NPM and pointing to deps.dev:version directly for other ecosystems. Concrete use cases like 'is X safe / popular / small' make the purpose unambiguous.

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 triggers: 'Use whenever an agent asks "is X safe / popular / small" or "what does adding lodash cost me"'. It also gives an exclusion and alternative: 'PyPI / Maven / Cargo / Go fall under deps.dev:version directly'. This clearly tells when to use this tool 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.