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

Annotations already set readOnlyHint, openWorldHint, and destructiveHint=false. The description goes further by detailing the failure mode of the OSV.dev query: when the query fails, isVulnerable is forced to false and vulnerabilityCheckFailed:true is the real signal. This is critical behavioral disclosure beyond annotations and prevents misinterpretation of a false negative.

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 longer than average but every sentence carries weight: purpose, key outputs, usage guidance, and failure-mode caveat. It is front-loaded with the core action and ends with the most nuanced edge case. No filler or 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?

Given the tool's complexity (registry metadata + vulnerability check), the description covers the essential return fields (isVulnerable, highestSeverity, findings with severity/summary/fixedVersion) and explicitly addresses the failure case. The output schema exists, so full enumeration isn't needed. An agent has everything necessary to call it correctly and interpret results accurately.

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 both name and version are fully described in the schema. The description adds context about the use case (lockfile pins) but doesn't add parameter-specific meaning beyond what the schema already provides. 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 states a specific verb ('Fetch registry metadata') and resource ('one exact version of a package'), then adds the secondary action of checking against OSV.dev. It distinguishes itself from siblings like get_package (latest release) and query_vulnerabilities by explicitly targeting exact pinned versions. No ambiguity.

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 an explicit when-to-use: 'Use this to check a version pinned in a lockfile rather than the latest release.' This clearly routes the agent away from using it for latest versions, implicitly pointing to alternatives. It also explains how to interpret edge-case failure behavior, adding operational guidance.

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