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

Annotations already declare readOnlyHint=true, and the description adds meaningful context beyond that: the source (weekly US Drought Monitor), the weighting formula (D0×0.1 through D4×1.0), and that updates are weekly. This gives the agent a better understanding of the tool's behavior and data freshness. No contradictions with annotations were found.

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 concise and front-loaded: the first sentence explains the main output and methodology, the second gives clear usage guidance, and the final 'Updates: weekly' is a useful, succinct detail. Every sentence earns its place with no wasted words.

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 read-only data retrieval tool with one optional parameter and no output schema, the description covers the key aspects: what it returns, the calculation, usage context, and update frequency. It does not describe response format, but without an output schema this is not strictly required. Missing minor details like rate limits or exact response structure prevent 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%, with the single optional parameter 'days' having a detailed description in the schema. The main description does not add any extra meaning about the parameter, so per the baseline rule for high schema coverage, a score of 3 is appropriate.

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 states the tool returns a 0-100 drought severity index with specific calculation details and includes week-over-week trend and D0-D4 coverage. It uses a specific verb ('Returns') and identifies the resource (US drought severity index). However, it does not explicitly differentiate from sibling tools, so it gets a 4 rather than a 5.

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 provides clear usage context: 'Call when the user asks how much of the US is in drought and how severe, or when timing agricultural hedging, water-supply, irrigation, or wildfire-exposure decisions.' This explicitly indicates when to use the tool. It does not mention alternatives or when not to use it, which would be needed for a 5, so a 4 is appropriate.

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