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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the safety profile is fully covered. The description's one genuine addition is the cost disclosure (10 credits, Tier 1), which is useful and not present in structured fields, but it says nothing about determinism or how 'allowReversed' affects the cast.

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 text is short and front-loaded with the spread meaning, and the cost tag earns its place. However, for a 5-parameter tool the description is undersized rather than efficiently concise — there is essentially no explanatory content beyond the spread name.

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 need no explanation, but the description omits critical invocation context: whether 'seed' makes the cast reproducible and what 'allowReversed' toggles (reversed rune meanings) are left entirely unexplained. For a divination tool with five optional parameters, this leaves the agent guessing.

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 only 40%: 'fields' and 'precision' are documented in the schema, but 'seed', 'question', and 'allowReversed' carry no explanation in either place. The description contributes zero parameter meaning, so it fails to compensate for the coverage gap.

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 states a specific resource and scope — a three-rune cast read as Past/Present/Future (Urdr/Verdandi/Skuld) — which implicitly distinguishes it from astroway_runes_single and astroway_runes_nine by cast size. It never uses an explicit verb ('cast'/'draw'), but the spread mapping is concrete enough to identify the tool.

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?

No when-to-use guidance and no alternatives named, despite obvious siblings (single, nine, by_zodiac). The Past/Present/Future framing weakly implies a situational reading, but nothing tells the agent when to pick this over the 1-rune or 9-rune cast.

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