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

With no annotations, the description carries the full behavioral burden, and it does contribute two useful facts: the call is paid at $0.1 per call and an API key is required. However, it says nothing about failure modes (e.g. what happens with a malformed period), rate limits, or whether the period must be the current month, leaving the safety profile thin.

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?

A single front-loaded clause names the tool's scope and its returned content, with a compact parenthetical for cost/auth. No filler, though the output enumeration is dense.

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 does outline the analytic content delivered. It remains incomplete on the two things an agent must decide on its own: how this differs from sibling fortune tools and what the period string must contain.

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 schema description coverage is 0% and the two required params (birth, period) have no inline descriptions, so the description must compensate. It partially does so by signaling the period format as YYYY-MM, but says nothing about the birth object beyond what the nested $defs already document.

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 resource (이달의 세운, this month's fortune) and scopes it precisely to the solar month (양력 월, YYYY-MM) measured by solar-term boundaries, then enumerates the outputs (월주·십신·일지 관계·좋은 날·주의 날). This is far more specific than a name restatement, though it never explicitly contrasts itself with siblings like unse or day_pillar.

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 statement of when to choose this tool over unse, day_pillar, saju_chart, or compatibility. Usage is only implicit from the word 'this month', and no exclusions or prerequisites are stated beyond the pricing/auth note.

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