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

Annotations already establish that this is a safe, read-only, idempotent operation. The description adds substantial behavioral context beyond that: the default search window, how weeks is populated or null, what unique/gap/overlap mean for planned_time, when shifted is true, and how utc resolves gaps versus overlaps, including the warning not to treat utc as the only reading.

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 front-loaded with the core purpose and then moves through defaults, output semantics, and caveats. It is dense and mostly earns its length, though some output-field explanations ('weeks is iso_week and us_week...', 'The change object and a planned time do not repeat the week numbers') are slightly convoluted and could be tightened.

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 complex DST tool with an output schema, the description covers the important gaps: default window, planned_time statuses, shifted behavior, utc resolution, and the warning about ambiguous times. An agent has enough information to invoke it correctly and interpret the key outputs.

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%, so the baseline is 3. The description adds useful semantics beyond the schema: from and to must be passed together or omitted together, the default window is today UTC through 365 days later, and planned_time is interpreted as a local wall time in the city. City matching behavior is already covered by the schema description.

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 gives a specific verb and resource: it says when a city's clocks next change and whether a planned local time is skipped or ambiguous. That planned-time ambiguity check distinguishes it in practice from the sibling get_dst_changes, but the description never names that sibling or explicitly states when to choose one over the other.

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 clear usage context: 'Use for a meeting time near a DST change, or a local time that may not exist or may be ambiguous.' It also explains the from/to pairing and the default 365-day window. It does not explicitly exclude cases or name alternative tools for plain clock-change listings.

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