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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, non-destructive, closed-world), so the bar is lower. The description adds useful behavioral context about what the cutoff parameter changes (it reports elapsed time), but with no output schema it never says what the return value looks like or how the timezone affects the response — a notable gap for a data-returning tool.

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?

Three short sentences with zero filler, and the core statement of what the tool is comes first. Every sentence carries information: identity, a use case for a parameter, and a when-to-call rule.

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 two-optional-parameter read tool with rich annotations, the description is nearly sufficient — purpose, trigger, and cutoff usage are all covered. The only shortfall is that without an output schema it should say what shape the date/time result takes.

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 coverage is 100% with per-parameter descriptions and examples (IANA tz, YYYY-MM cutoff formats). The description only motivates the cutoff parameter and never mentions tz at all, so it adds little meaning beyond the schema — the baseline 3 applies.

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 states exactly what the tool returns ('the real current date and time') and the word 'real' distinguishes it from the model's internal clock estimate — a distinction that matters for a tool with the ambiguous name 'now'. An agent knows precisely what it gets without opening the schema.

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 an explicit calling trigger: 'Call this before reasoning about anything recent,' plus a concrete secondary use case ('Pass your training cutoff to learn how much time has passed since it'). No sibling tools exist, so no alternative routing is required.

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