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

No annotations are provided, so the description carries the full behavioral burden. It discloses cost ($0.1/call) and authentication (API key required), which are important, but does not state whether the operation is read-only, whether it stores data, or how errors (beyond the schema's 422 for unknown city) are handled. For a computation tool with zero annotations, this is adequate but incomplete.

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 two compact sentences plus a parenthetical, with the core purpose front-loaded and no wasted words. Every clause adds useful information (scope, relation options, cost/auth).

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 tool's complexity (astrological compatibility from two detailed birth charts) and the presence of an output schema, the description covers purpose, relation variants, and practical constraints. It omits edge-case behavior and explicit alternative routing, but is largely sufficient for an agent to invoke it correctly.

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 0% at the top level, so the description must compensate. It adds meaning for the relation parameter by listing four relationship types and noting that ten-gods/roles/cautions are added, but it does not explain the a and b birth-chart inputs beyond '두 명식'. The nested AgentBirth schema does document fields, but the top-level parameters remain largely undescribed in the description.

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 the specific analysis (궁합) and its scope: two birth charts' day stems/branches harmony-clash and five-element complementation. It distinguishes from single-chart siblings like saju_chart by specifying '두 명식' (two charts), but does not explicitly name any sibling tool for negative 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?

The relation parameter options (연인|직장/동료|친구|사업 파트너) imply the tool is used for comparing two people in a specific relationship context, and the parenthetical notes prerequisites (paid $0.1/call, API key required). However, there is no explicit when-to-use versus alternatives or when-not-to-use guidance.

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