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

With no annotations provided, the description carries the full burden of behavioral disclosure. 'List' implies a read-only operation, which is helpful, but there is no mention of external API calls, freshness, availability, or potential failure modes. For a trivial zero-parameter getter this is acceptable but not rich.

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 core description is a single, front-loaded sentence with no wasted words. The empty '[COST: ]' prefix adds no value and slightly detracts from an otherwise clean, minimal description.

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 zero-parameter read-only tool with an output schema available, a one-sentence description is nearly sufficient. It lacks explicit behavioral caveats and sibling differentiation, but the low complexity means the description covers the essential information an agent needs to invoke it 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?

The tool has zero parameters and the schema is already fully self-describing with an empty properties object. The description therefore does not need to explain any parameter semantics; this is the baseline-4 scenario for a no-parameter tool.

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 uses a specific verb ('List') and a clear resource ('people currently in space'), so an agent immediately knows what data the tool returns. It also distinguishes itself from sibling tools like get_iss_location and get_space_news by identifying the exact subject matter.

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 implies the use case: use this tool when you need the list of people currently in space. However, it does not explicitly state when to prefer this tool over alternatives or mention any exclusions, so guidance is present only by implication.

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