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

No annotations and no output schema, so the description carries the full burden. It does disclose the core behavior (the exact arithmetic) and a pricing/trial constraint ('5 free trial calls per signed wallet'), but says nothing about units (days?), output shape, rounding, or how the string-typed inputs are parsed.

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 core definition is a single front-loaded sentence with zero waste; the trailing free-trial note is promotional but gives the agent pricing context. No 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?

For a simple 3-input calculator with no output schema or annotations, the formula covers the essentials, but missing units, output format, and the odd string-typed parameters leave an agent guessing about invocation details.

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 0%, so the description must compensate. It names all three parameters and assigns each a role with sign in the formula (payables subtracted), which is genuinely useful. However, it does not address that the schema types all three as strings or what format those strings should take.

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 ('Computes') and named resource ('cash conversion cycle'), and even spells out the formula (daysInventory + daysReceivables - daysPayables), which an agent can use to distinguish it from neighbors like x402-operating-cycle or x402-days-sales-outstanding. It stops short of explicitly differentiating from those siblings.

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?

There is no statement of when to use this tool, when not to, or which sibling to prefer (e.g., operating-cycle vs. this). Usage is only implied by the tool name and formula.

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