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

Beyond the annotations, the description discloses that start and end are the same instant, that unresolvable phrases return an empty candidates array, that timezone handling is DST-aware with a Europe/Berlin default, and that fabricating dates/time is forbidden. These behaviors materially shape agent reasoning and are consistent with readOnlyHint, openWorldHint, and destructiveHint.

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 well-structured and front-loaded with the purpose and no-call condition, and it uses clear sections for parameters, return behavior, and anti-fabrication rules. It is somewhat long and repeats the return shape a few times, so it is not maximally concise, but each block earns its place for a tool this complex.

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?

With no output schema, the description still explains the exact return shape (candidates[].datetime_range.{start,end}), clarifies the no-window behavior, specifies the empty-candidates failure mode, and delegates edge-case hour mapping to get_usage_guide. Nothing needed to invoke the tool or interpret its result is missing.

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 provides rich, 100%-coverage parameter descriptions covering text, lang defaults, tz IANA/DST semantics, and the format serialization. The description mostly restates these—text as written by the user, optional lang, optional tz—adding only marginal emphasis on using the raw user wording. Therefore it stays at the high-coverage baseline of 3.

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 operation and resource: resolving a time mention into an absolute ISO-8601 timestamp, with concrete examples and a clear no-call condition for full ISO-8601 inputs with offset. However, it does not explicitly contrast itself with sibling tools such as link_dynamic, so sibling differentiation is implicit rather than explicit.

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 gives explicit when-to-use guidance (natural-language time mentions, 'jetzt'/'now' as canonical current time), when-not-to-use guidance (complete ISO-8601 with offset), and what to do on failure (ask the user rather than computing). It also directs the agent to get_usage_guide for nuanced cases like hour mapping for vague dayparts.

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