Seller fee for one sale

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

With no annotations, the description carries the full burden. It usefully discloses one real behavioral default (Gumroad direct sales include 2.9% + $0.30 card processing unless overridden via the processing param) plus the US-seller/USD scope. It does not say whether this is a pure, side-effect-free calculation, what happens on invalid platform/param combinations, or whether any auth is needed.

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 sentences, front-loaded with the purpose and platform scope, then the one non-obvious default. No padding or repetition of the schema.

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?

There is no output schema, so the description usefully names the two return values ('fee and net amount'), which is the key thing a caller needs. For a computation tool with 2 required params and near-full schema coverage this is largely complete; the remaining gaps (error behavior, multi-currency beyond USD) are minor.

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 92% and four params are enums, so the schema already explains nearly everything (platform gating, defaults, per-platform semantics). The description only adds currency/region context and restates the Gumroad processing default, which is the correct baseline 3 when the schema does the heavy lifting.

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 names a specific computation (fee and net amount) for a specific resource (one sale) and enumerates the four supported platforms, so the agent knows exactly what it returns. It does not, however, differentiate itself from siblings like compare or price_for_target, so the agent must infer that 'one sale' means a single-calculation rather than a multi-scenario tool.

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?

Usage is implied rather than stated: the platform list, the '(US sellers, USD)' qualifier, and the Gumroad default give context for when the tool applies. There is no explicit 'use this instead of X' routing to compare, payout, or price_for_target, and no statement of what happens for unsupported regions/currencies.

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