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

With no annotations, the description carries the full burden of behavioral disclosure, but it only states the output. It does not explain whether the tool performs network calls, has side effects, or why it accepts parameters like 'ref', 'url', 'city', etc. The description is silent on these behaviors, leaving agents unaware of potential implications.

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 brief, almost to the point of under-specification. It consists of a single phrase and does not front-load any critical information beyond the basic output. While it has no wasted words, it omits essential context about parameters and usage, so it is not appropriately sized.

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 no output schema, no annotations, and a minimal description. It accepts nine optional parameters that are not explained in the description, and their behavior is unclear. An agent cannot determine what the tool actually does beyond returning a timestamp, making the definition incomplete for a tool with this complexity.

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 description coverage is 100%, so each parameter has a descriptive comment in the schema. Per the rubric, this yields a baseline of 3. The description itself adds no additional context about the parameters, but the schema already documents their purpose, so the description does not need to compensate. The parameters' oddity (e.g., a 'city' for a weather hint) is unexplained, but that gap is in the schema, not the description's responsibility.

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 'Current UTC timestamp' clearly states the tool's purpose: it returns the current UTC time. It is specific and not a tautology. However, it doesn't differentiate from the 'timezone' sibling, which might also provide time-related functionality, and it omits any mention of the nine parameters that are part of the input schema.

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 is provided on when to use this tool versus alternatives like 'timezone' or other utilities. There is no mention of prerequisites, typical use cases, or situations where another tool would be more appropriate. An agent has to infer usage entirely from the description.

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