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

The description adds valuable behavioral context beyond the annotations: it specifies that 11 mandatory holidays are returned, explains that Easter-dependent holidays are dynamically calculated using the Anonymous Gregorian algorithm, and describes the return structure. This is useful information not present in the readOnlyHint or idempotentHint 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 description is five sentences, each earning its place: it states the core function, details the output structure, quantifies the holidays, explains the algorithm, and gives usage guidance. It is front-loaded with the primary purpose and contains no fluff.

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 tool with one parameter and no output schema, the description is remarkably complete. It describes the output format explicitly, notes the exact count and algorithmic behavior, and provides a clear use case. The annotations cover safety and idempotency, so the description fully covers the remaining context.

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% for the single 'year' parameter, with a clear description ('Calendar year as a 4-digit integer. Example: 2026'). The tool description adds only 'for a given year,' which doesn't provide additional semantic value beyond the schema. Baseline 3 is appropriate for high schema coverage.

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 returns all French national public holidays for a given year as a structured list. It uses a specific verb ('Returns') and resource ('French national public holidays'), and distinguishes itself from sibling tools like get_portugal_holidays and get_spain_holidays by specifying 'French'.

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 provides clear usage context: 'Use when calculating French business deadlines, delivery dates, or scheduling tasks that must avoid non-working days in France.' It does not explicitly mention alternatives or when not to use the tool, but the context is sufficient for an agent to decide.

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