Calculate synastry - Relationship compatibility analysis API

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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering the safety profile. The description adds the output shape (compatibility score, inter-aspects with strength ratings, aspect counts, dynamics analysis) and the astrological tradition (Western tropical). It does not disclose edge-case behaviors like fallback for unknown birth times, but the schema addresses that. No contradiction with 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 is four sentences and front-loads the core purpose and method. The use-case sentence earns its place as context, but the closing claim "Based on professional astrological techniques" is filler and adds no functional 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?

Given the output schema, annotations, and detailed nested parameter descriptions, the definition is functional. The main gap is the lack of guidance for choosing between this and the closely related compatibility/composite tools, which matters in a large sibling set of astrology endpoints.

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?

Top-level person1 and person2 lack schema descriptions, resulting in 60% coverage; the description's phrase "between two natal charts" helps map those two undocumented parameters to the required inputs. The other parameters (lang, compact, houseSystem) and all nested fields already have detailed schema descriptions, so the description only partially compensates for the coverage gap.

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 states a specific verb ("Calculate"), a concrete resource ("synastry between two natal charts"), and a precise scope ("inter-chart aspects between all planets"). It clearly describes what the tool does, but it does not explicitly distinguish itself from the close sibling post_astrology_compatibility_score, which also handles relationship compatibility.

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 description provides implied usage context via concrete use cases ("dating apps, matrimonial sites, relationship counseling tools, and astrology compatibility features"). However, it never names alternatives or states when to prefer this over sibling tools like post_astrology_compatibility_score or post_astrology_composite_chart, so an agent has limited routing guidance.

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