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

With no annotations, the description carries the full behavioral burden and does disclose material traits: a hard operational quota ('FREE, limited to 30 readings per client per day') and the character of the response (terse völva voice, no modern comfort). It does not state read-only/reversibility or whether draws are randomized, which keeps it out of 5 territory.

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?

Front-loaded with the core identity and draw structure, then usage fit, then voice, then the quota. Every sentence carries information and none is filler. The 'Best for...' list is slightly long but each element is load-bearing.

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 single-parameter, no-output-schema tool, the description supplies what's missing structurally: the response's tone and framing (terse, no modern comfort) and the free quota. An agent can call it correctly and set caller expectations. Only the lack of explicit sibling routing leaves a gap.

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?

There is only one parameter ('question') and schema description coverage is 100%, so the baseline of 3 applies. The description names 'the question' as the input but adds no syntax, length, or formatting guidance beyond what the schema already documents.

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') and details the mechanism: a three-rune Urd/Verdandi/Skuld draw from the Elder Futhark in a völva's voice. This is far beyond a tautology and is inherently distinct from the sibling divination tools. It stops short of a 5 because it never explicitly contrasts itself against consult_tarot or consult_iching, leaving the sibling distinction to be inferred from the divination system named.

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?

'Best for the hidden force at work, what drives the situation beneath the surface, courage, transformation, and the shadow' gives explicit when-to-use guidance for question selection, which is more than implied usage. It stops short of 5 because there are no exclusions and no routing to the five sibling consult_* tools, so the agent must guess when runes beat tarot or iching.

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