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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, covering the safety profile. The description adds useful behavioral context by enumerating the specific data fields returned and including an example invocation. This goes beyond what annotations alone convey, though it does not address rate limits or error behavior.

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 two sentences: one functional summary and one example. It is front-loaded with the key purpose and wastes no words. Every sentence earns its place.

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 lookup tool with three parameters, good annotations, and no output schema, the description is complete enough. It tells the user exactly what data will be returned and gives a usable example. Minor gaps like default date behavior are already covered by the schema, not the description.

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 baseline is 3. The description includes a usage example showing q and dt, which reinforces the schema. However, the schema already thoroughly explains all three parameters, including the nuanced IATA code note for q. The description does not add 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 uses a specific verb ('Get') and clearly identifies the resource ('astronomy data') along with the key output fields (sunrise, sunset, moonrise, moonset, moon phase, moon illumination). This distinguishes it from sibling tools like current, forecast, and marine, which cover other weather domains.

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 states exactly when to use the tool: to retrieve astronomy data for a given location and date. It provides a concrete example with parameters, making the context clear. It does not explicitly mention when not to use it or name alternative tools, but the purpose is distinct enough that no exclusions are needed.

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