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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds meaningful behavioral context beyond annotations: the license/attribution requirement ('Data © IChing.Rocks — attribution is a condition of the license terms'), which is a non-obvious usage constraint. It also outlines the include levels, but those are also 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?

Two sentences: the first establishes the tool's core function and batch limit, the second covers the optional include levels and license. No filler words; information is front-loaded and every sentence earns its place.

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, the description does not need to explain return values. The schema covers parameters thoroughly, annotations cover safety, and the description adds licensing context. The only minor gap is not elaborating on invalid-id handling, but the schema's 'no duplicates, max 16 per call' covers the main constraint, making the description reasonably complete for this complexity level.

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 detailed parameter descriptions for both 'ids' and 'include'. The description repeats the include levels but adds no additional meaning beyond what the schema already provides, so the baseline of 3 is appropriate.

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 clearly states a specific verb ('Batch hexagram lookup') and resource ('hexagrams by King Wen numbers'), explicitly distinguishing this from its sibling tool 'get_hexagram' by the batch aspect ('max 16 ids per call').

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 provides clear usage context by noting it is a batch operation with a maximum of 16 ids, implying it is the tool to use for multiple hexagram lookups. However, it does not explicitly name alternative sibling tools or state when not to use this tool, so it stops short of a 5.

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