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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, so the safety profile is covered. The description adds real behavior beyond that: the 366-day maximum search span (not present in the schema) and the mechanism by which conditions are combined and offset. It does not state what the response looks like (list vs. count), which keeps it from a 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?

The purpose is stated in the first clause, followed by supported condition types, combination semantics, the offset mechanism, and one concrete example. Every sentence adds information an agent needs, and nothing is repeated from the schema verbatim.

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?

For a tool with five parameters and three parallel nested condition arrays, the description supplies the combination logic, the search-span limit, and offset semantics, which is enough to call it correctly. The remaining gap is the return shape (list of dates, count, per-condition matches) and its relationship to search_lucky_days; with no output schema, a sentence on results would complete it.

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 100%, and each nested condition field is documented in the schema with enums and examples, so the baseline is 3. The description does add meaning for all/any/none (すべて/どれか/除く) and for offset_days with the '翌日が満月'/'前日が祝日' illustrations, which the terse schema wording alone conveys less clearly.

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 opens with a specific verb and resource ('期間（366日まで）の中から、条件に合う日を探す'), and then enumerates the condition families (六曜・吉日・曜日・祝日・二十四節気・月相・日干支), so an agent immediately knows this is a multi-criteria date search, not a single-day lookup. It falls short of 5 because it never distinguishes itself from the sibling search_lucky_days, which plausibly overlaps with this tool.

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 description gives concrete guidance on how to invoke the tool: combine conditions with all/any/none, and use offset_days for shifted conditions such as '翌日が満月'. The worked example ('2027年の大安の土日で不成就日でない日') shows exactly the kind of query this tool is for. However, it never states when to prefer this over search_lucky_days or get_koyomi_day, and gives no exclusions.

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