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

Annotations already establish the safety profile (readOnly, idempotent, non-destructive, open-world), so the description is free to add non-obvious context — the weekly release schedule, that omission of dates returns the latest map, and that categories are cumulative (D1+ = D1 through D4). That cumulative semantics point is genuinely useful and not derivable from the schema.

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 tight sentences, front-loaded with what the tool returns before moving to cadence and the date default. No filler and nothing redundant with the schema.

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 must carry the return semantics, and it does explain the category breakdown and cumulative interpretation. It does not describe the shape of a range query response (e.g., one row per map date when start/end are given), which is a minor remaining gap.

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%, so all four parameters (state, measure, start_date, end_date) are already documented with formats and defaults. The description reinforces the date-omission default but adds no new parameter-level meaning beyond the schema, making the baseline 3 correct.

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?

Names a specific verb and resource ('Weekly U.S. Drought Monitor drought-severity statistics for one U.S. state or territory') and scopes it precisely to a single state, which cleanly separates it from the county and national siblings.

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?

Gives clear operating context: omit dates for the latest map, and the publication cadence (map valid Tuesday, released Thursday). It does not explicitly tell the agent when to prefer us_drought_county or us_drought_national over this tool, so it stops short of full alternative routing.

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