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

Annotations already declare readOnlyHint, idempotentHint and destructiveHint=false, so the safety profile is covered. The description usefully adds billing behavior (20 credits, Tier 2), which is real context not present in structured fields, but says nothing about output shape, computational cost, or failure modes beyond that.

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?

A single tight sentence with the key noun phrase front-loaded, followed by two short metadata tags. Nothing is redundant, though the bracket tags are boilerplate shared across the tool family rather than tool-specific value.

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 values need no explanation, and the nested birth-data schema is exhaustively documented. What remains missing is the routing information an agent needs to pick this tool over the near-identical midpoint sibling, leaving the definition only minimally sufficient.

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% with only 3 parameters, so the schema already carries the burden. The description mentions the orb and the focal-planet dimension, which maps loosely to the schema, but adds no format, default, or range detail beyond what is already documented.

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?

Names a specific verb (calculate) and a specific resource (Uranian midpoint trees / planetary pictures with symmetries), plus the scoping unit ('for each focal planet within a given orb'). It does not, however, distinguish itself from the sibling astroway_aspects_midpoints, which an agent could easily confuse it with.

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?

No when-to-use guidance, no prerequisites, and no reference to alternatives such as astroway_aspects_midpoints or astroway_aspects_antiscia. The only selection signal is the credit tier, which tells the agent about cost but not about appropriateness.

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