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

Annotations already set readOnlyHint=true and openWorldHint=false. The description adds meaningful context beyond that: data provenance ('scaled from NASA POWER root-zone soil wetness'), update cadence ('Updates: on source cadence'), and the list of return fields. No contradiction exists.

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 effectively three short sentences: what it does, when to use it, and update cadence. It is front-loaded with the core purpose, contains no redundant information, and every clause earns its place.

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?

Given one optional parameter and no output schema, the description is complete: it lists return fields, population coverage, source, and update cadence. The only parameter is fully documented in the schema, so an agent has all needed context to select and use this tool correctly.

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 sole parameter 'days' has a 100% schema description covering history, Gold tier requirement, and fallback behavior. The tool description itself says nothing about parameters, but since the schema does the heavy lifting, the baseline 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 opens with a specific verb ('Returns') and clearly identifies the resource ('0-100 agricultural moisture-stress score for any of 3,222 US counties'), plus the output fields. This unambiguously distinguishes it from the many opaque sibling names (e.g., adw.adw_001) and the title 'Agroclimate Stress Index' is consistent.

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 explicit 'Call when' guidance: drought, soil moisture, crop stress, growing conditions, and ag decisions like planting/irrigation/hedging/lending. This is clear and contextual, but it does not mention when not to use or name alternative tools, so it misses the top tier.

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