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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered structurally. The description contributes one piece of real context — the word 'effective' signals the output is a practical/attenuated figure rather than raw astronomical daylight — but does not explain what adjustments are applied or the precision of the estimate. With an output schema present, return format need not be described.

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 short sentences with the computational intent front-loaded and no filler. The trailing list_bundles pointer is only marginally on-topic for this specific tool, keeping it just short of ideal.

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 three-parameter, read-only calculation with a full-coverage schema, existing annotations and an output schema, the description covers what is needed to invoke it. The only real omission is disambiguation from the sun/solar siblings, which is a discoverability rather than invocation 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% with a documented enum for orientation, so the schema already carries full parameter meaning. The description merely restates the three parameter names without adding interpretation, such as how orientation maps to reduced hours or how latitude interacts with month. Baseline 3 applies when the schema does the heavy lifting.

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+resource ('Estimate effective daily sunlight hours for a garden') and the three determinant inputs, which is more precise than most sibling calculate_* names. However, it does not distinguish itself from nearby siblings such as calculate_sun_exposure or calculate_sunrise_sunset, so an agent must infer the boundary.

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 only usage-adjacent sentence points at list_bundles for 'jardinage' calculators, which is discovery guidance rather than when-to-use guidance. There is no statement of when this tool is preferable to calculate_sun_exposure or calculate_sunrise_sunset, and no prerequisites or exclusions.

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