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. It only states the core action and does not reveal that the nine parameters are optional and discarded, that the operation is read-only, or any details about the return format (e.g., ISO string, epoch). This leaves the agent without crucial behavioral context.

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 a single, focused sentence with no redundancy. It is maximally concise and front-loaded, containing exactly the essential information about the tool's purpose without any wasted language.

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 having 9 optional parameters and no output schema, the description does not explain how these parameters relate to the returned timestamp or what the return value looks like. The schema hints that parameters are discarded, but the description fails to tie this together, leaving the agent uncertain about correct invocation and result interpretation.

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 provides 100% coverage with clear descriptions for all 9 parameters (e.g., 'discarded after the shape check'), so the schema already handles parameter meaning. The tool description adds no extra parameter semantics, making the baseline of 3 appropriate. The description's silence on why parameters exist is a completeness issue, not a semantics one.

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' uses a specific verb ('Current') and resource ('UTC timestamp'), clearly identifying the tool's function. It is distinct from sibling tools like 'timezone' and 'iana-zones' in that it returns the current time rather than timezone metadata, though it does not explicitly differentiate itself.

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 lacks any mention of conditions, prerequisites, or exclusions, leaving the agent to infer usage solely from the name. This is a significant gap for a tool with many siblings.

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