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

Annotations are uninformative here (readOnlyHint=false on what is obviously a query tool), so the description carries the load and does so well: it defines the semantics of the "ok" result ("no listed flags, not a safety guarantee"), discloses a paid x402 flow at $0.002 USDC on Base charged per successful call, and notes the version parameter switches advisory source to deps.dev. None of that is in the structured fields.

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?

Dense and front-loaded: the returned fields come first, then caveats, ecosystem coverage, version behavior, alternative tool, and cost. Every sentence carries information, though the run-on field list and payment sentence make it heavier than it needs to be.

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 must enumerate return values, and it does (existence, version, release, age, downloads, licenses, deprecation, advisory severity) while also covering pricing and the sibling-tool boundary. An agent has everything needed to call it and interpret the response.

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 baseline is 3, but the description adds behavior beyond the schema: passing an exact version changes what metadata is returned and which advisory source is queried, and it reinforces that ranges/tags are not accepted. That is genuine added meaning over the property descriptions.

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 states a specific verb (reports) plus the exact resource attributes returned: existence, latest version/release, age, version count, npm weekly downloads, licenses, deprecation and advisory severity. It enumerates supported ecosystems and explicitly names the sibling it differs from (package-audit), so an agent can select it without inspecting either schema.

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?

It gives both a positive trigger ("Use before adding a dependency") and an explicit routing rule to an alternative ("use /package-audit for OSV affected ranges and dated FIRST EPSS CVE estimates"), plus the condition under which the optional version parameter changes behavior.

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