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

Annotations already declare readOnly/idempotent/non-destructive, so the safety bar is low; the description adds genuinely useful context the annotations lack, namely that calls are billed ('$0.005/call or Carry key'), which implies an auth/key requirement. It does not disclose pagination, default lookback, or return volume for a historical scan.

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 tight sentences, front-loaded with the useful part (the metric list) and no filler. Minor redundancy between 'Past extreme episodes' and 'what happened after past funding extremes'.

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?

With no output schema, the description usefully doubles as a return-value spec by naming the five metrics. However, for a parameterized historical scan it leaves the most decision-relevant facts unstated: what coin defaults to, what lookback window is used, and how 'extreme' is defined by min_abs_apr.

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 0% across three parameters, and the description explains none of them: 'coin' scope, 'days' (3–120 lookback window) and 'min_abs_apr' (the extreme-defining threshold) are left entirely opaque. The '4/12/24 h' horizons in the text are fixed output offsets, not the 'days' parameter, so they may even mislead.

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 resource ('past extreme episodes') and enumerates exactly what is returned: onset, hours above threshold, half-life, price return and funding accrued at 4/12/24h. The word 'past' implicitly separates it from the sibling carry_extremes, which scans for current extremes.

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 second sentence gives a clear use case: 'Use for what happened after past funding extremes (price, funding accrued, half-life).' It does not name the alternatives (carry_extremes, carry_history, brief) or state when not to use it, so routing still requires the agent to compare sibling names.

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