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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the description is free to add the genuinely new behavioral facts: it returns seven fit scores plus a per-rule breakdown for one investor, and the rules are invest-like's application of published criteria, 'never the investor's own opinion'. That disclaimer prevents a real misinterpretation. Cost, latency and data freshness are not mentioned.

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 trigger condition, then the return shape, then the caveat — no filler sentences. The parenthetical investor roster and example phrasings are long but each carries selection value, keeping it just shy of maximally tight.

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?

No output schema exists, so the description carries the full burden of describing returns — and it does, covering both the seven-investor score vector and the per-rule detail with real values and pass/fail. Combined with the 100%-covered input schema and safety annotations, an agent has everything needed to call it correctly.

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%, so the baseline is 3; the description earns above it by explaining what the optional investor parameter actually changes in the response ('for one named investor, each rule with the company's real value and whether it is met'), which the schema's one-line 'Show this investor's rules one by one' only hints at.

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?

Names a specific verb and resource ('check a stock against investors' published rulebooks') and immediately enumerates the seven rulebooks and what the result contains (0-100 fit per investor, per-rule detail for one). This lets an agent distinguish it from check_halal, check_value and explain_stock without opening a 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?

Opens with an explicit trigger: 'Use this when the user asks whether a stock fits a famous investor's style or rules', reinforced with three representative user phrasings. It does not name the sibling tools to use instead (e.g. check_value or check_halal) or state exclusions, so it stops just short of a 5.

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