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

Annotations already declare readOnly, idempotent, closed-world and non-destructive, so the safety profile is covered. The description adds two genuinely new facts — determinism (same question yields the same hexagram) and a 10-credit cost — but says nothing about output shape beyond what the output schema provides.

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 tight lines, with the core purpose front-loaded before the bracketed group and cost metadata. Nothing is padded, though the boilerplate bracket tags carry little decision value.

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?

An output schema exists, so return values needn't be described, and annotations cover the safety profile. What remains missing is sibling differentiation among five I Ching tools and any semantics for the required question input, leaving the agent to guess at routing.

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 coverage is 67%: fields and precision are documented in the schema, but the required 'question' parameter has no schema description and the tool description only says 'from question text', adding no constraints or format guidance (2-500 chars). Baseline 3 is appropriate, with a small gap on the required parameter.

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 output (a hexagram) derived from a specific input (question text), and 'deterministic' hints at how it differs from sibling tools like throw_coins. However, it never names a sibling, so an agent must infer the distinction rather than being told it.

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?

There is no explicit when-to-use guidance or routing against the four sibling I Ching tools (daily, lookup_number, throw_coins, with_changing_lines). The word 'deterministic' implicitly contrasts with a random-cast tool, but nothing tells the agent which condition selects this tool.

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