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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new behavior: the output is a link that launches an external viewer, it yields a printable plate, and no geocoding happens server-side. It does not say whether the link expires or how it is formatted, but with rich annotations this is adequate.

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?

Three short sentences, front-loaded with what is produced, followed by use cases and then the one hard constraint. No filler or restatement of the name.

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 read-only, single-shot link builder with a fully documented schema and no output schema, the description covers purpose, use cases, input expectation and the no-geocoding limitation. It leaves only minor details (link lifetime, what the viewer does with the plate) unstated, which is acceptable.

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 every parameter (including the date range, time default of 21:00, place-as-engraving-label, and degree units) is already documented in the schema. The description only reinforces that coordinates must be supplied by the caller, adding little beyond structured data — baseline 3.

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 artifact — 'Build a link that opens OrbitStudio Sky … as a 3D-printable star map plate' — plus the exact inputs that define it (place on Earth, local date/time). It also implicitly separates itself from the place-lookup sibling by stating it will not resolve place names.

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?

Gives concrete occasions (birth, wedding, 'night we met') and an explicit exclusion: 'Give the coordinates yourself; this tool does not look up place names.' It stops short of naming search_places as the alternative for geocoding, so the routing rule is implied rather than stated.

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