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

Annotations already establish readOnly/idempotent/non-destructive behavior, and the description adds substantial context: retrograde awareness, default planets, forward/retrograde flags, final_settling semantics, data-only output, and range cap. This goes well beyond what annotations alone communicate.

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 compact and front-loaded with the core action. It slightly repeats what the schema already states (default planets and ~5-year cap), but the repetition is brief and useful as a caution. No wasted filler sentences.

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?

Even without an output schema, the description explains what returned data looks like: every sign change, retrograde back-out/re-entry, flags, and final_settling. Combined with schema-covered parameters and safety annotations, an agent has enough context to select and invoke the 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?

Schema description coverage is 100%, so the schema already documents all five parameters. The description reinforces the planets default and date-range cap but does not add meaningful parameter-level semantics beyond the schema, which matches the baseline for high schema coverage.

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 states a specific operation—sign-change/ingress dates for one or more planets across a date range—and clarifies the exact resource: sidereal sign changes, including retrograde back-out/re-entry and final_settling. The title and phrase 'Use for when does Saturn/Jupiter change sign timing' distinguish it from general transit or current-position sibling tools.

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 explicitly gives a use case: 'Use for when does Saturn/Jupiter change sign timing.' It also sets expectations with 'Data only' and a ~5-year range cap. It does not explicitly name alternative tools or state when not to use it, so it stops short of a full 5.

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