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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description adds valuable behavioral details: caching interval (6-hour), data source (FIRST.org), and the specific return fields (epss and percentile), surpassing what annotations cover.

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 concise yet comprehensive: front-loaded purpose, then parameter, returns, thresholds, integration advice, source, cache, and an example. Every sentence adds value without 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?

For a simple read-only tool with one parameter, the description covers all essential aspects: what it does, how to use it, what it returns, practical thresholds, and complementary tool recommendation. The presence of an output schema (not shown) further reduces the need for return format details.

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% with a brief description for cve_id. The description adds an example value and explains the return format, thresholds, and usage context, which enriches the parameter meaning beyond the schema baseline.

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 clearly states the tool fetches the EPSS exploit probability score for a CVE, predicting exploitation likelihood in the next 30 days. It distinguishes its role from sibling tools like security_fetch_cve_detail by contrasting EPSS (urgency) with CVSS (severity).

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 advises combining with security_fetch_cve_detail to prioritize patching, clarifying when to use this tool. It also provides threshold-based action guidance. However, it does not explicitly exclude scenarios where this tool should not be used, 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.