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

With no annotations supplied, the description carries the disclosure burden itself; it usefully states the timezone (UTC) and the exact data shape returned per station (sign and degree), which goes beyond a bare label. However, it says nothing about the underlying data source/precision, whether results are cached or computed on demand, or the result ordering, so an agent still lacks operational context.

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?

Two sentences, front-loaded with the resource definition before the usage hints, and no filler. Every clause (units, planets, years, example queries) carries information an agent needs.

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 two-parameter, read-only lookup with no output schema, the description covers scope, units, and returned fields well enough to call correctly. The single gap is the 2024/2025-2027 boundary mismatch, which could mislead a year-scoped call.

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 coverage is 100%, so both parameters are already documented, and the description only restates the planet list and a year window. Worse, it states the coverage as 2025-2027 while the schema allows 2024-2027, leaving ambiguous what a 2024 request returns.

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 names a precise resource (retrograde start and end/station times), its formatting (UTC, sign, degree), its planetary coverage (Mercury through Saturn), and its temporal window (2025-2027). This is unmistakably distinct from siblings like get_sign_ingresses or get_current_sky without needing to name them.

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 quoted example queries ("when is Mercury retrograde", "is Mercury retrograde now") give an agent a clear trigger for selecting this tool. There are no exclusions or named alternatives for adjacent questions, which keeps it 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.