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

Annotations already declare this as a safe read-only, idempotent operation. The description adds useful behavior beyond that: results are ordered by date, empty series should be returned when no history exists, and malformed CVE IDs should be corrected before calling.

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 front-loaded and clearly structured with headers and bullets. It is somewhat longer than necessary for a one-parameter tool, and the Outputs section is partly redundant because an output schema exists.

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 CVE history lookup, the description is complete: it covers purpose, usage, alternatives, input expectations, output shape, and empty-result behavior. No critical agent-facing information 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?

The schema has 100% coverage and already documents cve_id as a CVE-YYYY-NNNNN string. The description reinforces that format and adds validation behavior for malformed or incomplete IDs, plus guidance to call once per CVE when multiple are mentioned.

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 and resource: getting the historical EPSS time series for a specific CVE. It also explicitly distinguishes this from the sibling tool vulnerability_score by saying to use that tool for the current EPSS score.

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 concrete user intents that should trigger this tool, such as EPSS trend questions, spiking/dropping, and historical comparisons. It names an alternative tool for current-score questions and covers multi-CVE and malformed-CVE handling.

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