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

The description adds meaningful behavioral context beyond the readOnlyHint annotation by detailing the formula (20-day tail-exceedance rate vs 252-day baseline, sigmoid-scaled), the 0-100 score range, the output fields, and the daily refresh. It does not contradict annotations and provides a richer picture of what the tool returns and how it behaves.

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 description is front-loaded with a dense, informative first sentence that explains exactly what the tool returns. However, 'Updates: daily.' at the end redundantly repeats 'refreshed daily' from the first sentence, so not every sentence earns its place, preventing a 5.

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?

Without an output schema, the description is responsible for explaining return values. It lists the output fields (score, trend, confidence, top_drivers, tail_prob_shift, tail_prob_recent, tail_prob_baseline) but does not explain what 'trend', 'confidence', or 'top_drivers' represent. The optional history behavior is only in the schema, not in the description, leaving some gaps for a moderately complex tool.

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?

The schema provides 100% coverage of the only parameter ('days'), including its optional nature, range, and Gold tier requirement. The main description does not add parameter semantics, so the baseline score of 3 is appropriate—the schema is doing the heavy lifting.

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 clearly states a specific verb and resource: 'Returns a 0-100 fat-tail risk escalation score for US equities' with calculation details, making its purpose unambiguous. However, it does not explicitly distinguish itself from sibling tools by naming alternatives or contrasting with other risk metrics, so it falls short of a 5.

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?

The description provides an explicit 'call when' list covering tail risk, fat tails, crash probability, extreme moves, volatility regime shifts, drawdown risk, and timing de-risking/hedging. This gives clear context for use, but it lacks explicit when-not-to-use scenarios or alternative tool suggestions, so it earns a 4 rather than a 5.

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