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

Annotations already declare readOnly, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description adds genuine value beyond that: it discloses the auth model (anonymous keyless vs. keyed personalized rate) and edge-case behavior (what happens when nothing sells or a delivery fails).

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 dense sentence that front-loads the trigger ('Before you sell') and enumerates the outputs compactly. Efficient and mostly earns its place, though the nested parenthetical creates slight reading friction.

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?

With no output schema, the description carries the return-value burden and does so by enumerating the computed components (fees, reseller share, failure outcomes). Combined with the auth note, an agent has enough to call and interpret it, leaving only minor parameter-semantics gaps.

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 33%, so the description must compensate. It references 'a price' and 'reseller share,' loosely mapping to price_minor and reseller_share_pct, but gives no units/format guidance for the undocumented params and is silent on currency selection. Partial compensation only.

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 computational purpose: a fee breakdown for one paid sale (platform fee, reseller share, Stripe card fee range) plus listing fee and failure/no-sale outcomes. It is clearly distinct from siblings like sales_statement or price_hint, though the verb is implied ('what ... leaves you') rather than stated crisply.

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?

Gives clear timing context ('Before you sell') and conditional behavior ('No key needed; with a key you see your own rate'), telling the agent both when to call it and how auth changes the result. It does not name an explicit alternative sibling or exclusion, so it falls 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.