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

With no annotations, the description must disclose behavioral traits. It only states the basic function, but the schema shows 9 parameters that are all discarded after various checks. The description fails to disclose that all parameters are ignored and that the tool simply returns the current time. This is a significant omission for a tool with such a generic parameter set.

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 concise at only two words, but it is under-specified. It does not provide structure or context beyond the bare function. While it is not verbose, it fails to earn its place by omitting essential details about parameter behavior and use cases.

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 description is far from complete. With 9 optional parameters, no required fields, and no output schema, the agent needs context on why these parameters exist and how they are used. The description gives no indication that they are discarded, leaving the tool's behavior ambiguous. This is a significant gap for a tool with such a complex schema.

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%, with each parameter having a description that explicitly states it is discarded (e.g., 'discarded after the shape check'). The tool description adds nothing about parameters, but the schema already provides full semantics. Since the schema covers all parameters, the baseline of 3 is appropriate.

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 distinguishes from sibling tools like 'timezone' which likely deals with timezone conversions, and 'iana-zones' which lists zones. However, it lacks a verb like 'get' or 'return', making it a noun phrase, but the intent is unambiguous.

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 no guidance on when to use this tool versus alternatives. It does not mention any prerequisites, exclusions, or comparisons to sibling tools. An agent has no information about the context in which this tool is preferred.

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