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

With no annotations provided, the description carries the full burden of behavioral disclosure. It does a good job by specifying the line-value encoding (6,7,8,9), the bottom-to-top order, the condition for a changing hexagram, and the determinism effect of seed. It stops short of describing error cases or the exact JSON response shape, but the core runtime behavior is transparent enough.

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 description is two sentences with no filler. The first sentence leads with the action and the key outputs; the second sentence adds an optional-parameter nuance. Every clause earns its place, and the structure is front-loaded for an agent to quickly understand purpose.

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?

Given three optional parameters and no output schema, the description covers the essential return semantics (primary hexagram, line values, moving lines, changing hexagram) and an important behavioral knob (seed). It could be slightly more complete by mentioning how the result is structured or how 'method' affects probabilities, but those details are already in the schema, so this is sufficiently complete for casting a hexagram.

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?

All three parameters are fully described in the input schema (100% coverage), so the baseline is 3. The description adds extra value for the seed parameter by explaining its purpose ('deterministic... useful for testing or reproducing a reading'), which goes beyond the schema's terse 'Optional seed for deterministic casting.' The method and question parameters are already well covered by the schema, so no additional description is necessary.

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 'Cast a hexagram for an I-Ching consultation,' which is a specific verb+resource pairing that clearly distinguishes this tool from the lookup siblings (lookup_hexagram, lookup_yilin). It also enumerates the returned artifacts (primary hexagram, lines, moving lines, changing hexagram), making the tool's function unmistakable.

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 context is implied: the tool is for I-Ching consultations, and the seed parameter is explicitly positioned for testing/reproducing readings. However, it never contrasts itself with the sibling tools (e.g., 'use lookup_hexagram to inspect a known hexagram' or 'use divine for a broader reading'), so the when-to-use vs alternatives guidance remains implicit rather than explicit.

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