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

No annotations are provided, so the description must disclose behavior. It only states a simple calculation, but it is unclear if the tool is read-only, whether errors occur for invalid input, or what side effects exist. The description is too terse to cover behavioral aspects.

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 extremely short (one clause), which is concise, but it is under-specification rather than appropriate conciseness. It lacks necessary context for an agent to understand the tool's purpose.

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?

Despite 100% schema coverage, the description contradicts the parameter semantics and provides almost no information. The combination of a vague description and irrelevant parameters makes the tool unusable for correct invocation.

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?

None of the 9 parameters in the schema logically relate to 'Unix day-of-year from seconds'; they are unrelated (e.g., 'ref', 'url', 'city', 'json'). The description does not explain how any parameter is used; it appears disconnected from the schema.

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 says 'Unix day-of-year from seconds' which implies a conversion from seconds to day-of-year, but it does not specify what input parameter is used or what output to expect. It lacks a clear verb and resource, making it ambiguous. It does not differentiate from sibling tools like timezone or utc-time.

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?

No guidance on when to use this tool versus alternatives. The description does not mention any context for usage, such as converting a Unix timestamp to day-of-year, nor does it exclude alternatives. Sibling names do not clarify the distinction.

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