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

No annotations are present, so the description must disclose all behavioral traits. It states the output (current UTC timestamp) but fails to mention that the nine optional parameters are validation-only and discarded after checks, as implied by the schema. This is a significant omission because an agent might assume the parameters affect the timestamp or are required for some operation. The description does not contradict annotations (there are none), but it leaves out critical 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 extremely concise—one sentence—and front-loads the core purpose. It contains no filler or redundancy. However, it might be too under-specified for a tool with a complex parameter schema, but the schema itself handles parameter documentation. The conciseness is appropriate for stating the primary function.

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 tool's complexity (9 optional parameters, no output schema, no annotations), the description is far too minimal. It does not explain that the parameters are validation-only and that the output is always the current UTC time regardless of inputs. An agent reading only the description would not know how to use the parameters or what the response format is. The schema provides parameter details, but the description fails to tie them together or set expectations for the return value.

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 detailed descriptions for all 9 parameters, including notes like 'discarded after the shape check', so the schema already clarifies parameter semantics. The tool description adds no additional meaning about parameters, which is acceptable given the schema's completeness. The baseline of 3 applies because the description does not compensate for any schema gaps, but none exist.

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 primary purpose: retrieving the current UTC time. It is specific enough to distinguish from timezone-related tools, though it does not explicitly mention that it is distinct from the 'timezone' sibling, which might handle conversions. The verb-resource pairing is clear.

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 that 'timezone' or 'iana-zones' might be more appropriate for timezone conversions, nor does it specify any conditions or exclusions. An agent would have to infer usage purely from the name and the one-line description.

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