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

Goes well beyond the annotations: discloses a 30/hour per-client rate limit, that results are summary-only (a truncation constraint on the return), survivorship-bias-free and point-in-time universe construction, and the window bounds. These are exactly the operational facts annotations cannot express, and none of them contradict readOnlyHint=true or idempotentHint=true.

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 compact clauses, front-loaded with what the tool is, followed by the alternative and the rate limit. Every element — window, universe, output scope, price comparison, quota — carries information an agent needs; nothing is wasted.

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 only two parameters, an output schema present, and full annotation coverage, the description supplies the operational context (cost, quota, output granularity) that structured fields cannot. The only material omission is enumerating the available strategy types, which the schema union names but does not explain.

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 `days` parameter is restated with its 14..90 bounds, which the schema already documents. The `strategy` parameter — the one effectively lacking a schema-level description, driving coverage to 50% — is only characterized as 'any strategy'; the four discriminated types (breakout, momentum, dip, ma_trend) are never named or differentiated in the description, which is the main gap it should have filled.

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+resource (a free sample backtest) and pins the scope precisely: point-in-time top-10 universe, `days` window 14..90, summary-only output. It explicitly positions itself against the sibling `backtest`, so an agent can distinguish the two without opening either schema.

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?

Names the alternative (`backtest`, $0.05) and the condition that selects it implicitly via 'free sample' vs 'full version', plus the hard constraint of 30/hour. It never states when NOT to use this tool (e.g., that the sample is unusable for production-grade or long-window analysis beyond summary level), so it stops short of full explicit when/when-not guidance.

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