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

Annotations already declare readOnlyHint and idempotentHint, so the safety profile is covered. The description adds meaningful behavioral context beyond that: the response shape (CVSS versions, CWE, CPE, KEV, references), the 100-ID cap, and a concrete size warning about 1MB+ responses. This goes beyond the minimum expected.

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?

Three tightly written sentences with no filler. The core action and scope come first, followed by return-value summary, then the capacity warning and parameter recommendation. Every sentence earns its place.

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 read-only lookup tool with a rich output schema and full parameter documentation, the description is complete. It covers the main operational caveat (response size for large batches), the ID limit, and the available fields. Nothing needed to call 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 coverage is 100%, so the baseline is 3. The description adds practical semantics for the brief parameter by recommending it for batches over 10 IDs and explaining the context-budget rationale. This provides value above the schema's default-value description, justifying a 4.

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 opens with a specific verb and resource: 'Fetch one or more CVEs by ID from the NIST National Vulnerability Database.' It enumerates the returned data (CVSS versions, CWE, CPE, KEV, references), making the tool's role unmistakable and clearly distinct from the search-oriented 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 states this tool is for fetching by CVE ID, which implies it should be used when IDs are already known, distinguishing it from nvd_search_cves. It also gives explicit guidance for bulk usage: 'For bulk lookups of more than 10 IDs, use brief: true.' It lacks an explicit 'when not to use' or named alternatives, but the context is clear.

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