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

Annotations already declare readOnly, idempotent, non-destructive and closed-world behavior, so the safety profile is covered. The description adds a genuinely useful constraint beyond structured data: it operates purely on supplied numbers with no market-data fetch, which reinforces the closed-world hint and tells the agent it can rely on self-contained input.

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?

A single front-loaded sentence led by the verb and resource, with the capability enumeration and the self-containment constraint packed into clauses that each earn their place. No filler or redundancy.

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?

An output schema exists, so return values need not be explained, and the single parameter is well covered by the schema. The only minor gap is that input phrasing (how to express odds/prices in freeform text) is not illustrated, which for a broad multi-mode calculator would help an agent form a valid call.

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?

With one parameter at 100% schema coverage, the schema already carries the definition ('The reader's words, with their numbers'). The description's 'numbers you supply' / 'typed odds' / 'typed prices' phrasing adds marginal color but no syntax or format guidance beyond the schema, so baseline 3 applies.

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 ('runs a betting calculation') and enumerates the concrete modes (odds conversion, implied probability, payout, no-vig, hold, breakeven, parlay, arb/hedge). It also distinguishes itself from market-data siblings with 'Uses only the numbers given, no market data,' though the arb/hedge mode hints at overlap with the 'arbs' sibling that isn't addressed.

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 list of calculation modes implies when an agent would reach for this tool, and the 'no market data' clause signals it is for pure computation rather than lookup. However, there is no explicit when-to-use/when-not or named alternative (e.g., arbs vs. this tool's arb split), so routing is left to inference.

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