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

Annotations already declare it as a safe, read-only, idempotent operation. The description adds valuable domain context: that station estimates aren't exact-to-the-second, and that it includes shadows and uncertainty windows. It also mentions privacy/data-handling, which is extra. It doesn't contradict annotations.

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 mixes useful scoping with a privacy notice and a caveat about precision. The privacy sentence feels tangential and could be omitted or moved. Front-loaded with the core purpose but somewhat cluttered.

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?

Given output schema exists, the description doesn't need to explain return values. It covers scope, limitations (station accuracy), and includes examples. Missing explicit guidance on the 'lang' parameter, but overall complete for a simple lookup tool.

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 only 33%; the description names 'planet' and 'year' and gives a range for planets, but doesn't explain the 'lang' parameter or its fallback behavior (though the schema does describe lang). Baseline 3 is appropriate as schema handles some but not all, and description adds marginal detail on planet scope.

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?

Clear verb+resource+scope: 'Find retrograde periods by planet and year', with concrete example queries and the planet/date range (Mercury through Pluto, 1900–2099). This is distinguishable from sibling tools like get_planet_positions or get_sign_ingresses.

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?

Provides natural-language example queries that imply when to use it, and the scope (planet, year, 1900–2099) clarifies coverage. However, it doesn't explicitly state when to use siblings instead (e.g., get_planet_positions for daily positions), so it stops short of full alternative routing.

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