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

With no annotations provided, the description carries the full burden. It discloses the return structure (series with date, score, percentile, model), ordering by date, and handles the empty-series edge case. However, it does not explicitly state that the tool is read-only or describe any potential side effects, which is a minor gap for a retrieval tool.

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 well-structured with clear headers: purpose, when to use, inputs, outputs, and LLM guidelines. It is detailed but not verbose; each sentence serves a purpose, and the most critical information is front-loaded.

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?

The tool has only one parameter, an output schema, and no annotations. The description covers everything needed: what the tool does, when to use it, input format, output structure, and edge-case behavior (no history). It also distinguishes from a sibling tool, making it contextually complete.

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 CVE format ('CVE-YYYY-NNNNN') and providing guidance on handling malformed IDs (asking the user to correct). This goes beyond the schema's minimal description.

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: 'Get the historical EPSS time series for a specific CVE.' It clearly identifies the tool's scope (historical time series) and differentiates from the sibling `vulnerability_score` by explicitly stating that tool covers current EPSS scores.

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?

Includes a dedicated 'When to use this tool' section listing concrete user intents (e.g., 'EPSS trend over time', 'whether EPSS spiked or dropped') and provides an explicit alternative: 'If the user only wants the current EPSS score, use `vulnerability_score` instead.' Also includes LLM-specific directives like never guessing values and handling malformed CVE IDs.

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