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

With no annotations, the description carries full behavioral disclosure. It reveals output tone ('terse, grounded, offers no modern comfort'), the interpretive persona (Norse völva), and a concrete cost (0.10 via x402). It does not explicitly describe the response format or whether runes are random, but it covers the major usage-impacting behaviors.

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?

Every sentence brings new information: the draw type, the interpretive voice, the best use cases, the tone, and the cost. No filler, and the most defining mechanics appear first.

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?

For a one-parameter tool with no annotations and no output schema, the description covers what the tool does, how it behaves stylistically, who it is for, and the cost. It stops short of clearly stating the shape of the returned reading, which would make it fully complete, but the invocation path is clear.

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 100% and the single 'question' parameter is adequately documented in the schema. The description reinforces that the question is what gets consulted but adds no additional parameter-level syntax, constraints, or examples, so 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: 'Consult the Runes' with a clear mechanism ('three-rune draw... Elder Futhark') and interpretive style. This firmly distinguishes it from sibling divination tools like tarot or iching.

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?

Provides explicit suitability guidance ('Best for the hidden force at work, what drives the situation beneath the surface, courage, transformation, and the shadow') and contextualizes the voice ('no modern comfort'). Does not explicitly name when not to use or compare alternatives, hence not a 5.

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