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

Annotations already declare readOnlyHint=true and idempotentHint=true, covering the safety profile. The description adds the important behavioral condition that data requires attribution ('Data © IChing.Rocks — attribution is a condition of the license terms'), which is not captured in annotations. It also clarifies the nesting semantics of include levels, though that is largely in the schema.

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?

Four short sentences, each earning its place: purpose, parameter options, sibling alternatives, and license notice. The most decision-relevant information is front-loaded, with no redundancy or filler.

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 simple read tool with two parameters and an output schema, the description fully covers what the tool does, detailed include behavior, sibling selection, and legal constraints. The output schema covers return values, so further description is unnecessary.

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%, with both id and include fully documented including default and meaning of each level. The description repeats the values (summary, core, lines, full) without adding new syntax or format details beyond the schema, so the baseline 3 applies.

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 'One hexagram by King Wen number (1-64)', clearly stating a specific verb (get) and resource (hexagram) with its key parameter. It explicitly differentiates from siblings by contrasting with get_hexagrams (several), get_all_hexagrams (entire set), and search_hexagrams, making the singular scope unambiguous.

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 explicitly names sibling tools and their use cases: 'get_hexagrams for several numbers at once, get_all_hexagrams for the entire set, search_hexagrams to find hexagrams by text, and get_reading_context for a changing-line reading.' This tells the agent exactly when to prefer this tool over alternatives, and the include parameter options define usage depth.

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