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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is covered. The description adds valuable behavioral context by disclosing the free tier limit of 25 calls/day per IP and the paid x402 rate, though it does not describe error behavior or pagination.

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 definition is front-loaded and compact: the vulnerability lookup purpose comes first, followed by a separate pricing/limit sentence. Every phrase contributes useful information, and there is no redundant filler.

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?

For a five-parameter tool without an output schema, the description compensates by listing the returned fields and documenting cost limits. It still omits the key invocation constraint that at least one package identifier is expected and how purl/package/version interact, but the complete schema coverage fills most remaining gaps.

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 schema already documents all five parameters. The description reinforces the package/version use case and ecosystem coverage but does not add parameter-specific rules such as whether purl takes precedence over package or when version should be omitted.

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 that it retrieves known vulnerabilities for an open-source package version from OSV.dev, names the covered ecosystems and sources, and lists the returned fields. This is specific enough for an agent to know exactly what resource it provides, and it is clearly distinct from unrelated sibling tools.

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 implies the tool is used when checking a package version for known vulnerabilities, but it does not give explicit when-to-use/when-not-to-use guidance. It also does not explain the relationship between the purl, package, version, and ecosystem parameters, leaving selection logic to the schema.

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