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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so the safety profile is covered. The description adds useful non-annotation context (Elder Futhark group, 10-credit Tier 1 cost), but says nothing about what the Pennick layout produces or how the question/seed influence the reading.

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 short, front-loaded lines with zero filler; the cost and group metadata are bracketed and skimmable. The brevity is efficient, though it shades into under-specification rather than tightness.

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 for a 5-parameter divination tool with three undocumented inputs the description leaves too much open: it never says whether `seed` makes the cast reproducible, what `question` does, or what `allowReversed` changes in the reading.

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 only 40%: `fields` and `precision` are documented, but `seed`, `question`, and `allowReversed` have no schema descriptions. The description mentions no parameters at all, so it fails to compensate for the gap on three undocumented inputs, including the domain-significant allowReversed flag.

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: a cast of 9 runes using the Pennick layout. This is clear enough to identify the operation, but it never distinguishes itself from the sibling rune casts (astroway_runes_single, astroway_runes_three, astroway_runes_by_zodiac) beyond the implicit count in the name.

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 statement of when to choose this 9-rune cast over the single- or three-rune siblings, nor any prerequisites or context for use. The agent must infer selection purely from the tool name.

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