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 disclose the returned payload in unusual detail (trigram composition, judgment in Chinese plus Legge translation, six line texts, plain-language meaning, source link). It omits failure/ambiguity behavior, such as what happens with an unmatched or ambiguous name.

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?

Two sentences, both dense with information, with the identification methods front-loaded before the return-value summary. No filler or redundancy.

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 no output schema, the description must explain returns and does so thoroughly, making it complete for a single-parameter lookup tool. It lacks only edge-case handling (invalid/ambiguous identifiers) to be fully self-sufficient.

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% and the schema's own description already gives concrete examples ("乾"/"qián"/"Force"/"The Creative"), so the description's listing of number/Chinese/pinyin/English largely restates structured data. Baseline 3 applies; it adds no new constraints or format guidance 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?

The description names a specific verb and resource ("Look up ... hexagram") and enumerates the accepted identifier forms (King Wen number 1-64, Chinese name, pinyin, Wilhelm English name). It reads as an identifier-based retrieval tool, implicitly distinct from cast_hexagram and list_hexagrams, but it never names or explicitly contrasts those siblings.

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?

Usage is implied: use this when you already have a hexagram identifier to resolve. There is no explicit when-to-use/when-not statement and no routing guidance toward cast_hexagram or list_hexagrams for the cases where the user doesn't yet have a number or name.

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