Set an input_datetime value

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

Annotations already declare non-readOnly, idempotent, non-destructive behavior; the description adds real value on top: it names the underlying `input_datetime.set_datetime` HTTP call and discloses the notable edge case that passing none of date/time/datetime still invokes the service with only entity_id.

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?

Front-loaded purpose sentence followed by two tight supporting sentences. Slightly padded by a 'Returns:' line that duplicates information already available via the output schema, but otherwise no waste.

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 an output schema present and 100% schema coverage, the description doesn't need to explain returns or parameter formats; it correctly focuses on the edge-case behavior and usage condition. Slight redundancy in the Returns line keeps it from a 5.

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 description coverage is 100%, including formats and the datetime-overrides-date/time precedence rule, so the description's 'whichever of date, time, datetime are given' adds no detail beyond the schema. 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?

States a specific verb and resource ('Set an input_datetime helper's date, time or combined datetime value') and pins the target helper type, which cleanly separates it from the many sibling helpers_set_input_boolean/number/text/select tools without needing 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?

Explicit 'Use when: writing a specific date/time to an input_datetime helper' gives the triggering condition. It doesn't name an alternative tool by name, but the sibling set is already partitioned by helper type, so the context is clear.

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