Synastry (Two-Chart Comparison)

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

Discloses behavioral traits beyond annotations: mentions that missing birth_time reduces house/ascendant accuracy, and describes privacy_mode levels. No contradiction with annotations (readOnlyHint, idempotentHint, destructiveHint).

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?

Three sentences with clear structure: main purpose, then prerequisites, then options. No redundant information; every sentence earns its place.

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 tool with 6 parameters, nested objects, and output schema, the description covers prerequisite resolution, optional parameters, and edge cases (missing birth_time). Complete given available context.

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 description adds value by explaining usage (e.g., resolve with astral_search_birthplace, privacy_mode meanings, response_format options). Enhances understanding beyond schema alone.

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 clearly states the tool compares two birth charts (synastry) and returns inter-chart aspects, scored dimensions, and an overall score. It distinguishes from sibling tools like astral_compute_natal_chart (single chart) and astral_current_transits.

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 instructs to resolve city names with astral_search_birthplace first and provides guidance on privacy_mode options. Lacks explicit when-not-to-use scenarios, but the context is generally clear.

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