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

The readOnlyHint annotation already establishes that this is a safe, non-mutating operation. The description adds meaningful behavioral context beyond annotations: the formula, the assumption that legs are independent and all win, and the 21+ entertainment disclaimer. It does not describe the exact response structure or error behavior, so it stops short of a 5.

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 the core payout formula and constraint, then follows with assumptions and disclaimers. It is dense but appropriately sized; the legal/entertainment disclaimer is relevant but slightly lengthens an otherwise compact definition.

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?

Given the readOnly annotation, high schema coverage, and no output schema, the description provides enough context to call the tool correctly. It defines the computed outputs (payout, profit, implied probability) and assumptions, though it does not specify the exact response shape or error handling.

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 100%, so the schema already documents both parameters. The description reinforces the 2 to 20 leg constraint and clarifies that decimal odds are multiplied, but it does not add syntax or format details beyond the schema.

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 states a specific verb and resource: computing the payout of a parlay with 2 to 20 legs. It clearly defines the calculation, including combined odds and implied probability. It does not explicitly differentiate itself from siblings such as convert_odds or expected_value, which keeps it from 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 usage is implied by 'Payout of a parlay ... that all win' and the 2 to 20 leg constraint, but there is no explicit guidance on when to use this tool versus alternatives like convert_odds or expected_value. No when-not conditions are provided.

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