Synastry

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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds meaningful behavioral context beyond that: concrete orb thresholds per aspect type and an explicit disclaimer that the result is a descriptive tally, not a compatibility score, which manages output expectations.

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 dense sentence that front-loads the core action and then enumerates outputs in a clear parenthetical list. It is information-rich with no filler, though the length slightly favors completeness over brevity.

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 steps in to describe return content (aspects with orbs, planet-in-house placements, tally), and the input schema fully documents the two nested birth-data parameters. Combined with annotations covering safety, an agent has everything needed to call it correctly.

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 are richly documented nested objects (date, time, city shortcut, coordinates, timezone, house_system), so the schema carries the semantic load. The description adds only a passing reference to Ascendant implying time may matter, which the schema already explains in more detail.

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 ('Compare') and resource ('two natal charts'), and immediately scopes the output: major aspects, house overlays, and a descriptive tally. The 'two charts' framing cleanly separates it from the single-chart natal_chart sibling without needing to name it.

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 purpose implies the use case (relationship/relational analysis between two people), but there is no explicit when-to-use guidance, no exclusions, and no pointer to alternatives such as natal_chart for a single person or transits. Usage is inferred rather than stated.

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