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

Annotations already cover read-only/idempotent/closed-world, but the description adds real behavioral context beyond them: UTC precision to the minute, the default-to-current-year behavior, and the notable edge case that a period crossing the year boundary is shown in full. It also declares scope limits (describes positions, does not predict events or give advice) and an attribution requirement.

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?

Core capability is front-loaded in the first sentence and the usage/alternative guidance follows logically. It runs slightly long with the boilerplate disclaimer and attribution sentences, but each carries a real constraint the agent must honor.

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?

An output schema exists, so return structure need not be explained. Between the description and schema, an agent has scope, defaults, edge-case handling, sibling routing, and compliance obligations - nothing needed to call it 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 coverage is 100% and the single parameter's range (1900-2100) and default are fully documented in the schema itself. The description's 'year is optional and defaults to the current year' restates what the schema already says, adding no new syntax or format meaning.

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 ('Lists the retrograde periods of Mercury, Venus, Mars...') and immediately distinguishes its scope from siblings by naming get_transits and get_transits_to_chart. An agent can tell exactly what this returns without opening the schema.

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?

Explicitly enumerates the triggering questions ('whether a planet is retrograde on a date, when a Mercury retrograde starts or ends, which planets are retrograde in a year') and routes two adjacent use cases to named alternative tools. Nothing is left to inference.

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