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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description usefully adds that output is Fahrenheit-basis with included Celsius-basis totals, which is real behavioral context. However it says nothing about the output format or how results are structured, so it is only mildly additive.

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?

Two compact sentences with no padding, and the core action is front-loaded. The 'Fahrenheit basis' / 'Celsius-basis totals' phrasing is slightly dense but earns its place by conveying units.

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 stateless read-only calculator with full schema coverage and annotations handling the safety profile, the description covers inputs and hints at the dual-unit output. It is largely complete, with only the exact return structure unstated, which is acceptable given no output schema exists.

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 schema already documents all five parameters, setting a baseline of 3. The description goes slightly beyond by mapping 'growing, heating, or cooling' to the mode enum and clarifying the temperature basis, adding marginal semantic value.

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 (Accumulate) and resource (growing/heating/cooling degree days), naming the three computation modes in plain terms. There are no closely related siblings among the calculators, so no sibling differentiation is needed. Clear but not maximally precise about the computational method.

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 implies the inputs needed (daily high, low, base, day count) but gives no explicit when-to-use guidance or how to choose among the gdd/hdd/cdd modes. Usage is only inferable from the mode enum in the schema. No alternatives or exclusions are offered.

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