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 key behavioral traits: uses a real rule-based engine, covers 206 countries, computes moveable holidays astronomically (not guessed), and costs $0.01 USDC per call. These go beyond the basic schema and inform the agent about accuracy, breadth, and cost. It does not mention error handling or rate limits, but that is not essential for a read-only lookup 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 three sentences long, front-loaded with the primary action, and every sentence contributes value: the first defines the purpose and scope, the second emphasizes accuracy, and the third discloses the cost. There is no redundancy or filler. It is appropriately concise for the tool's complexity.

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?

Given the output schema exists, the description does not need to explain return values. The description covers the core purpose, geographic coverage, accuracy, and cost, which are the most relevant contextual factors for agent decision-making. It does not mention caveats like invalid inputs or region/state dependencies, but the schema already details parameter constraints. Overall, it is complete for a simple lookup tool with robust structured metadata.

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 covers all 6 parameters with 100% description coverage, so the baseline is 3. The description adds minimal semantic value by summarizing that the tool works for a 'country (and optionally a state/region) and year' and mentions 'public/bank/school holidays' which implicitly maps to the `types` parameter. It does not provide any additional meaning beyond what the schema already offers, but does not contradict it either.

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 looks up 'real public/bank/school holidays' for a country (and optionally state/region) and year, with a specific verb 'looks up' and resource 'rule-based calendar engine covering 206 countries'. It distinguishes itself from guessing or approximate data by emphasizing accuracy and astronomical computation. Although there are no sibling tools to differentiate from, the purpose is unambiguous and specific.

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 gives clear context for when to use the tool: when you need genuine holiday data for a country/state/year, backed by a reliable engine. It also discloses the $0.01 cost, implying an economic consideration for use. It does not explicitly mention alternatives or exclusions, but no sibling tools exist, and the straightforward lookup context suffices. The 'not guessed' clause reinforces reliability, making the intended use clear.

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