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

The annotations already establish that this is a safe, read-only, idempotent, non-destructive operation. The description adds substantial behavioral context beyond annotations: it computes real star positions, handles local time including time zones and DST, returns a preview and multiple vector poster formats, and explicitly notes that it takes a city rather than coordinates.

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 front-loaded with the primary use case and remains dense with useful detail. Each sentence contributes either usage guidance, behavioral capability, input constraint, or scope limitation, and there is no wasted filler.

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?

Given the tool's complexity, full schema coverage, annotations, and an output schema, the description is complete enough for correct invocation. It covers the main purpose, input constraint, behavioral scope, output formats, and exclusions without needing to explain return values in detail.

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 nine parameters with examples, defaults, and constraints. The description reinforces that the city must be a name rather than coordinates and that local time is handled, but it does not add much parameter-level meaning beyond the schema.

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 verb and resource: generating a star map or night sky poster for a date and place, with concrete examples. It is clear, but it does not explicitly differentiate itself from the sibling generate_moon_poster tool, so it falls short of the top score despite strong specificity.

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 gives clear when-to-use conditions (birthday, wedding, anniversary, the night they met, or tonight) and when-not-to-use cases (not planets, not navigation, not telescope pointing). It does not name alternatives among the sibling tools, so it stops short of a 5.

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