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

Annotations already cover the safety profile (readOnly, idempotent, closed-world). The description adds real behavioral context beyond them: the scoring inputs, the 'five best days first' output ordering, and the '(API Pro)' plan requirement — none of which appear in the annotations.

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 tight sentences, front-loaded with the primary behavior before the actionability hint. The parenthetical list of factors and activity values is dense but each element is load-bearing.

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 usefully sketches the return shape (per-day scores, five best first). For a nested-object, read-only tool this is largely sufficient, though the required birth-chart input could be noted more explicitly.

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 40%, so the description must compensate. It enumerates the eight activity values and the 62-day window bound (mapping to `to`), but says nothing about the required nested `birth` object or the top-level `timezone`, which the description only implicitly references. Partial compensation at the baseline.

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 and resource: every day of a window scored for one activity, with the computed factors (transits, Moon phase/sign, void of course) and the result ordering (five best first). This distinguishes it cleanly from siblings like best_cities and daily_transits without opening a schema.

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?

Explicitly frames the use case: 'Use it to pick dates for an activity within the next weeks,' and the window bound clarifies the intended horizon. It gives clear context but does not name an alternative tool or state when NOT to use it.

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