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

Annotations already provide readOnlyHint and idempotentHint, indicating safe read-only behavior. The description adds valuable context: orbit speed (28,000 km/h), orbital period (90 minutes), and update frequency (~60 seconds). This goes beyond annotations without contradicting them.

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 concise sentences with no redundant information. The first sentence front-loads the core purpose and returned data. The following sentences add context without wordiness.

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 retrieval tool with one parameter and an output schema (implied), the description covers the returned fields, update frequency, and orbit characteristics. It provides most necessary context, though it could mention the data source or any usage limitations.

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?

Input schema coverage is 100% with one optional parameter 'units' that has a description and enum. The description adds no additional meaning beyond what the schema already provides, so baseline score of 3 is appropriate.

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 clearly states the tool retrieves the real-time position of the ISS and lists the specific data fields returned (latitude, longitude, altitude, velocity, daylight/eclipse visibility). It is specific enough to distinguish from general space tools, though it does not explicitly differentiate from the sibling 'iss.space.tle' tool.

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?

No explicit guidance on when to use this tool versus alternatives. It mentions update frequency (~60 seconds) which hints at real-time use, but does not specify when it's appropriate or provide comparisons to other ISS or position-related tools.

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