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

Adds substantial context beyond the annotations: billing model ($0.01/call via x402 USDC or card key, first 25 free, failed calls free) and an explicit no-side-effect statement that reinforces readOnlyHint. 'Each call is charged, so repeats are not free' meaningfully explains the idempotentHint=false finding rather than leaving the agent to guess. It does not disclose update cadence or caching, which is the remaining gap.

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?

Front-loads the core payload (what the position includes) in the first clause, then use cases, then commercial terms. Dense but every sentence carries information; the pricing clause is long but is genuinely decision-relevant for a paid call.

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?

With no output schema, the description does the work of naming the returned fields and the upstream source, which is enough to interpret a result. Missing freshness/latency expectations and whether values are cached, which for a 'current position' tool an agent may care about.

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 single optional 'only' projection parameter is fully documented in the schema at 100% coverage, so the description can rely on it. The description itself adds no meaning about the parameter, which is acceptable at this coverage level but is a missed opportunity for a low-cost optimization hint.

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 resource (International Space Station) and enumerates exactly what is returned: latitude, longitude, altitude, speed, and daylight status. No sibling tool covers orbital/satellite data, so an agent can distinguish it immediately; the data source (wheretheiss.at) is also named.

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 usage contexts (space apps, education bots, sky-watching alerts) which tell an agent the kind of request this fits. It stops short of explicit when-not-to-use guidance or naming an alternative, but with no comparable sibling in the list there is little to disambiguate against.

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