format_time

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

With no annotations provided, the description carries the full burden, and it does contribute the guarantee that formatting is 'deterministically' performed and lists broad format support. However, it does not disclose timezone handling, invalid-input behavior, default calendar/locale semantics, or what the returned string looks like, leaving notable behavioral gaps.

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 short and front-loaded, with the purpose in the first sentence and format capabilities in the second. The final sentence about Intl.DateTimeFormat is slightly implementation-oriented and could be removed, but overall the structure wastes little space.

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 5-parameter tool with no annotations and no output schema, the description is too thin to be fully actionable: it omits timezone semantics, output form, error behavior, and how to route between this and the related temporal siblings. An agent would likely need to inspect parameter defaults or experiment to invoke it confidently.

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?

With only 40% schema description coverage, the description partially compensates by naming locale examples (en-US, de-DE, ja-JP, fa-IR) and mentioning Jalali and custom Luxon formats. It still leaves timezone semantics essentially undocumented and adds little beyond the schema's already-detailed format and datetime property descriptions.

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 clearly identifies the operation as 'Deterministically format a datetime string' and enumerates the supported output families (ISO 8601, RFC 3339, locale-aware, Jalali, human-readable, and custom Luxon formats), so an agent can understand the core purpose. It does not explicitly contrast it with sibling tools like convert_time or resolve_time, but 'format' as the verb is sufficiently distinct.

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?

No when-to-use versus alternatives is given; there are no exclusions or routing conditions relative to convert_time, now, resolve_time, or other siblings. The only instruction-like sentence, 'Use Intl.DateTimeFormat for locale-specific output,' appears to describe an implementation detail rather than when an agent should select this tool.

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