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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so safety behavior is covered. The description adds useful non-schema context — the 10-credit Tier 1 cost and the endpoint — plus the fact that either a King Wen number or six line values are accepted. It does not disclose what happens if both inputs are supplied or what errors occur on invalid line counts.

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?

One dense but well-ordered sentence front-loads the accepted input, then walks through the outputs; the group/endpoint/cost block is compact structural metadata. No sentence is filler, and the parenthetical glosses ('upper over lower', 'lines 2-4 and 3-5', 'every line changed') prevent ambiguity cheaply.

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 and fully documented parameters, the core is covered, and enumerating return fields is arguably redundant but harmless. The remaining gap is sibling disambiguation inside a very large I Ching tool family and the unspecified interaction when both `hexagram` and `lines` are provided.

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%, so the baseline is 3, but the description adds real meaning the schema lacks: it establishes that `hexagram` and `lines` are alternative ways to specify the same hexagram rather than additive filters. It still does not state precedence when both are passed.

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 concrete resource and enumerates the exact derived outputs (two trigrams, image ordering, five-phase relation, nuclear trigrams/hexagram, inverse, complement), so an agent knows precisely what analysis it produces. However, it never distinguishes itself from the closely-named siblings astroway_iching_trigrams or astroway_iching_lookup_number, leaving overlap ambiguous.

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 only usage framing is 'For a hexagram (number or lines),' which is input guidance, not routing guidance. There is no statement of when to prefer this tool over astroway_iching_trigrams, astroway_iching_lookup_number, or astroway_iching_reading, and no exclusions or prerequisites.

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