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

Annotations already cover read-only, idempotent, open-world and non-destructive semantics. The description adds genuinely non-structured traits: the data source (OSV.dev and its aggregated feeds), the per-call price with a 10/day free tier and x402 payment-required result, and error behavior (isError, not charged). Return format is left to the output schema, which is reasonable.

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 but front-loaded: capability, data source, batch usage, when-to-use, pricing, errors. Every sentence carries information, though the pricing/error clauses make it slightly long for a lookup tool.

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?

An output schema exists, so return values need not be described. The description fully covers scope, batch semantics, alternatives, cost, and failure modes — nothing an agent needs to invoke it correctly is missing.

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 description coverage is 100%, so the baseline is 3, but the description adds real semantic value the schema lacks: the batch string syntax 'ecosystem:name@version', the intent (auditing a lockfile), and the up-to-50 constraint framed as a workflow rather than a bare maxItems.

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?

States a specific verb+resource (vulnerability lookup for a package version) and enumerates the returned content: severity, CVE/GHSA ids, and fixed version. It also names the supported ecosystems, which pins down scope precisely.

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 routes the agent: 'When to use: For CVEs in one package version; for general package facts use package_info' — naming the alternative and the condition that selects it, including the sibling's server. This is exactly the when/when-not/alternative structure.

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