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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds genuinely useful context the annotations don't carry: the 10-credit cost, the POST endpoint, and the fact that a numeric 0-100 score is returned. It says nothing about failure modes or input validation, so it is adequate rather than rich.

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 core sentence is front-loaded and dense, and the bracketed metadata lines (group, endpoint, required, cost) are compact and scannable. Minor redundancy in repeating the required parameters, but nothing is verbose or wasted.

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?

An output schema exists, so return values needn't be explained, and the description still helpfully notes the 0-100 score. However, for a two-person nested-object tool it omits any when-to-use routing and leaves the person date inputs semantically unexplained, so it is minimally viable rather than complete.

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 50%: fields and precision are documented in the schema, but person1/person2 (nested date objects with only a regex pattern) are not. The description merely restates 'Required: person1, person2', which the schema already declares, and adds no semantic detail about date format or the person objects, so it does not compensate 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 names a specific result (pair compatibility), the method (Tzolkin name + tone alignment plus elemental/directional affinity), and the output shape (0-100 score), which distinguishes it from sibling Mayan tools like tzolkin, haab, or full. It stops short of explicitly contrasting itself with those siblings, so it is clear but not fully differentiated.

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?

No guidance on when to prefer this over astroway_mayan_full, astroway_mayan_tzolkin, or other compatibility-style tools. The only routing signal is the bracketed 'Required: person1, person2' metadata, which is not a usage condition.

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