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

Annotations already mark the tool as read-only and idempotent; the description adds valuable behavioral context on top: it is a true external-clock call, requires no API key or account, returns both ISO 8601 and Unix timestamp, and accepts IANA/offset timezones. It does not contradict the annotations.

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?

Every sentence earns its place: purpose/output, usage guidance, auth/directness, and parameter semantics are each covered in a compact four-sentence structure with no filler. The key action is front-loaded in the first sentence.

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?

For a simple single-optional-parameter tool with an output schema and safe annotations, the description is complete: it covers what, when, why, auth, and parameter behavior. The output schema handles return-value details, so the description need not repeat them.

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 already fully documents the timezone parameter with a default and example formats at 100% coverage. The description paraphrases that same meaning ('IANA name or a fixed UTC offset and defaults to UTC'), adding little value beyond the schema.

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 opens with a specific verb and resource ('Get the true current date and time') and names the concrete return forms (ISO 8601 string and Unix timestamp). It also scopes the tool to any timezone, clearly distinguishing it from unrelated sibling tools such as generate_uuid.

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?

It gives explicit when-to-use guidance ('whenever the actual present moment matters') with concrete examples like stamping records, computing ages/deadlines, and expiration checks. It also explains why an LLM should not guess the time, making the guidance actionable and unambiguous.

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