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

Goes well beyond the annotations: caching (up to an hour), the 100-result cap, latency (~1 s), pricing ($0.001), the shared free-tier pool across skypeek routes, and the exact failure mode (503 upstream_unavailable, not charged, retry later). For a read-only open-world call these operational traits are exactly what an agent needs and the annotations cannot supply.

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 purpose, then inputs, then data provenance, limits, caching, errors, latency and price — a sensible ordering. It is dense and some material (NASA endorsement disclaimer) reads as boilerplate, but nearly every sentence carries actionable information.

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 enumerates the return fields (designation, approach time, distance with 3-sigma range, velocity, magnitude, diameter), plus caps, caching and error semantics. Nothing an agent needs to call this correctly is missing.

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% and both parameters already document their ranges and defaults in the schema, so the description's restatement of `days` and `dist_max_au` adds little. Baseline 3 is appropriate since the schema carries the semantic load.

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 verb and resource ('near-Earth object close approaches to Earth in the next 1-30 days within a miss distance') and enumerates the returned fields. An agent can distinguish this from nearby siblings like satellite_passes and aurora_forecast purely from the description.

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 clear scope (1-30 day look-ahead, default miss distance) and an explicit exclusion ('Not an impact-risk assessment'), which steers the agent away from a plausible misuse. It does not name a sibling alternative or spell out when this is preferred over other astronomy routes, so it falls short of a 5.

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