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

Annotations already establish read-only, idempotent, non-destructive, non-open-world behavior, so the safety profile is covered. The description adds two genuinely non-obvious facts: the score scale (0-100) and the metered cost (10 credits, Tier 1), plus the methodology. It says nothing about what happens with missing birth times or how the score is composed.

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?

One front-loaded sentence carries the whole meaning, followed by structured group/cost tags that are metadata rather than prose. Nothing is redundant; the only mild cost is that the tags occupy lines that could hold input guidance.

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 an output schema present, return values needn't be described, and annotations cover safety. What is missing is any input-side context for a nested two-person tool with 40% schema coverage – no note that birth dates are required or that time is optional.

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 only 40%: person1.date, person2.date, time, language, and solarYear carry no schema description, and the description compensates for none of them. It never states that the tool takes two people's birth dates as its core input, leaving the required nested persons objects to be discovered from the schema.

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 resource (pair compatibility score), the output range (0-100), and the exact doctrinal basis (San He trine + Liu Chong conflict-pair canon), which is unusually precise. It does not name or differentiate itself from the nearest siblings (astroway_chinese_zodiac_animal, astroway_horoscope_compatibility, astroway_relational_match_score), so it falls short of a 5.

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?

There is no when-to-use guidance, no exclusions, and no mention of alternatives such as the Vedic ashtakoot or Western synastry compatibility tools. The agent must infer from the name and canon alone that this is the Chinese-zodiac-specific pairing tool.

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