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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description adds useful context: it shows the real current sky from the darkest observatory site, includes specific sky contents, and explicitly says nothing is stored. It does not cover latency, errors, or failure behavior, but it adds solid behavioral context beyond 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?

The description is compact and largely front-loaded, moving from the overall sky view to the optional target behavior. The atmospheric phrase 'where it is always night' is flavorful but does not obscure the operational meaning.

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 simple one-optional-parameter tool with annotations and no output schema, the description is complete enough: it covers the default sky view, targeted viewing, examples of valid targets, and the fact that nothing is stored.

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 100%, so the schema already documents the optional target parameter. The description still adds meaning by giving target categories and concrete examples such as the moon, a planet, 'pleiades', 'orion-nebula', and 'andromeda-galaxy'.

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: look at the real sky right now through a telescope, including moon phase, visible planets, and brightest stars. It clearly distinguishes this astronomical/observatory experience from sibling tools such as walk_in_the_forest or visit_the_museum.

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 explains the two modes: without target, see the sky and what is up; with target, look at that object. However, it does not explicitly say when to choose this tool over related contemplative siblings, so usage is implied rather than fully guided.

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