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

Annotations already cover readOnlyHint, idempotentHint, openWorldHint, and destructiveHint. The description reinforces these and adds useful context beyond them: the source is 'CISA KEV catalog (updated daily, cached)' and the result answers whether the CVE is actively exploited. This adds meaningful provenance and staleness context without contradicting annotations.

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 first sentence is front-loaded and clear, followed by a logical flow: safety, parameter, return fields, source, alternative tools, fallback. Some redundancy exists—'Read-only. No side effects. Idempotent.' largely repeats annotations, and the report_feedback instruction is verbose—but the description is still well-organized and not bloated.

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 only one parameter, an output schema, and comprehensive annotations, the description covers everything needed for correct invocation: exact parameter format, return fields, source and freshness, semantic interpretation, and routing to sibling tools. Nothing essential is missing for an agent to decide when and how to call this tool.

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 value by specifying the exact CVE identifier format 'CVE-YYYY-NNNNN' with example 'CVE-2021-44228', and confirming it is required. This is more explicit than the schema's brief 'e.g. CVE-2021-44228' and helps prevent malformed invocations.

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 object: 'Check whether a CVE is in the CISA Known Exploited Vulnerabilities (KEV) catalog.' This clearly identifies the resource and the boolean nature of the query, and it distinguishes the tool from related CVEs tools by emphasizing KEV's unique role in answering active-exploitation triage.

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 explicitly routes to alternatives: 'Use security_fetch_cve_detail for full CVE severity. Use security_fetch_cve_epss for exploit probability.' It also states why KEV is the right choice (active exploitation question not available in NVD), and even provides a report_feedback fallback if the tool fails to satisfy the user.

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