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

The description does not disclose that all input parameters are discarded, nor does it explain the purpose of the oddly named parameters such as 'Git ref name' or 'JSON text to validate'. Without annotations, the description carries the full burden, and it fails to clarify the tool's real behavior beyond returning a timestamp.

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 short sentence, which is efficient and front-loaded. However, it is terse to the point of under-specification—concise but missing critical context about the parameter behavior. It earns a 4 for being compact, but not a 5 because it omits important information.

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 complex input schema with seven seemingly irrelevant parameters and no output schema, the one-line description is insufficient. It does not explain that the tool can be called with no arguments, that all parameters are ignored, or what the return format (e.g., epoch seconds vs. ISO string) looks like. The definition is incomplete 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?

The input schema provides descriptions for all seven parameters, but those descriptions are confusing in the context of a UTC timestamp tool (e.g., 'discarded after the shape check'). The description adds no clarification or additional meaning beyond what the schema already states, so it stays at the baseline for high schema coverage.

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.' states a specific verb (returns) and resource (UTC timestamp). It is clear about the core functionality, but does not explicitly distinguish it from sibling tools like timezone or iana-zones, so it doesn't fully earn a 5.

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?

There is no guidance about when to use this tool versus alternatives. No mention of when not to use it, no reference to timezone or iana-zones, and no indication whether arguments should be passed. An agent is left to infer usage from the schema alone.

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