Compatibility score - Relationship compatibility API

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

Annotations declare readOnlyHint=true and destructiveHint=false, so the safety profile is already known. The description adds useful context about the return categories (romantic, emotional, etc.) and specific planetary pairs, but does not disclose any additional behavior such as error handling, rate limits, or edge cases. Since output schema exists, return format details are not required here. The description adds moderate value beyond 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 one focused paragraph that front-loads the core purpose ('Calculate a detailed compatibility score...') and then enumerates the breakdowns. It is detailed but not bloated, with each sentence contributing useful information about output composition. Slightly longer than necessary but well-structured.

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 read-only tool with a rich input schema and an output schema (indicated), the description covers the key aspects: what it returns (score, categories, narratives, elements, archetypes, aspects). It does not mention when to choose this over the sibling post_astrology_synastry, which is a notable gap given the tool list. Otherwise, it is complete for the given complexity.

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 detailed descriptions for person1, person2, lang, and compact. The tool description itself adds no parameter-specific information beyond what the schema already provides, so it does not elevate the semantics. Baseline of 3 is appropriate.

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?

Clearly states it calculates a detailed compatibility score between two birth charts using Western synastry, with specific verb and resource. It lists return contents, but does not explicitly distinguish itself from the sibling post_astrology_synastry, which also likely deals with inter-chart aspects. Thus it is clear but lacks explicit sibling differentiation.

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?

Provides no guidance on when to use this tool versus alternatives like post_astrology_synastry or post_astrology_composite_chart. It does not state when not to use it or mention any prerequisites beyond the required input. The agent must infer its applicability from the name and description alone.

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