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

Annotations already declare read-only, idempotent, non-destructive behavior, so the safety profile is covered. The description adds real context: 'input ignored' (the cast is not parameterized), the sunset date, and a 10-credit cost. It stops short of describing the random/seedless nature of the cast beyond the implicit contrast with the seeded replacement.

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 deprecation warning is front-loaded, which is correct, but it is repeated three times (title, description opener, and the trailing bracket block). Group/Endpoint/Cost metadata and the ⚠️ footer add bulk that competes with the routing message.

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, return values need no explanation, and the deprecation, replacement routing, cost, and sunset are all stated. Nothing an agent needs in order to avoid or correctly invoke this tool is missing.

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 both params (fields, precision) are already documented as compact-mode output shapers. The description adds only the indirect note that input is ignored, which slightly conflicts in spirit with the presence of params, but no syntax or semantics are added beyond the schema. 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?

States a specific verb and resource ('Casts a single I Ching hexagram') and explicitly positions itself against the entire /iching/* sibling namespace, listing each replacement and its distinguishing trait. An agent can tell this apart from astroway_iching_throw_coins without opening a schema.

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?

Explicitly says when NOT to use it (deprecated, sunset 2027-06-16, avoid) and names six concrete alternatives with their differing capabilities. Nothing is left to inference about routing.

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