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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior, so the safety profile is covered. The description adds real operational context beyond that: the step/range ceiling interaction, the required parameters, and the 100-credit Tier 4 cost, which the agent needs for budgeting. It stops short of describing pagination or response truncation on long ranges.

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?

Front-loaded with the core behavior, then a compact block of required/endpoint/cost metadata. Every line carries information; the only slight redundancy is restating the required parameters that are already evident from the schema.

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 an output schema present, return values need no explanation, and the description covers the constraints that matter for a ranged computation tool — step floor, range ceilings, optional planet filter, and cost. Only minor gaps remain around date format and behavior on very long ranges.

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 only 33%: fields and precision carry their own descriptions, but startDate, endDate, stepDays and planetIds are undocumented in the schema. The description partially compensates by giving the stepDays unit floor and marking planetIds as an optional filter, but adds nothing about date format or step defaults.

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 names a specific verb and resource — return planet positions over a date range with a configurable step — and adds scoping constraints (min step, max range). It is clearly distinguishable from single-moment siblings like astroway_western_planets, though it never names an alternative explicitly.

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?

It states hard operating limits (step min 0.01 days; 1-year cap for sub-day steps, 5 years otherwise) and notes planetIds is optional, which helps the agent use it correctly. However, it gives no when-to-use-vs-siblings guidance, e.g. when to prefer a single-chart planets call over a ranged ephemeris.

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