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

Annotations already cover read-only/non-destructive/open-world, and the description adds genuinely non-obvious behavior: the horoscope body is NOT returned and must be read from item.url at the Hankyoreh original. The Korea-time default is also useful context. No error/empty-result behavior is described, keeping it below 5.

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?

Three sentences, front-loaded with the usage triggers, then the return-scope caveat, then the date default. Every sentence carries information; only the URL caveat is somewhat verbose.

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 fields need not be explained, and the description still proactively sets expectations that the body lives behind item.url — critical because the tool name implies it returns horoscope content. Nothing essential for calling it correctly is missing, though the relation to get_mbti_horoscope is unstated.

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 100%, so the schema already documents the single optional date parameter, its YYYY-MM-DD format and the today-in-Korea default. The description only restates that same information, adding little beyond 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 verb+resource ('그날의 운세' 조회) and clarifies the surprising part of the contract: it returns only title/publish date/original URL, not the horoscope text itself. It indirectly separates itself from get_mbti_horoscope via '띠별 운세', but never names that sibling, so the differentiation is only implied.

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?

Gives concrete trigger phrasings ('오늘의 운세', '오늘 운세 알려줘', '띠별 운세') and states the default (today, Korea time) plus how to override. It does not say when to prefer get_mbti_horoscope instead, so a sibling-choice edge case is left to inference.

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