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

Annotations already cover the safety profile (readOnlyHint=true, destructiveHint=false), and the description adds genuinely non-structured information: the credit cost per successful call, that repeat calls may be recharged, and that returned data should be treated as untrusted. The billing note is consistent with idempotentHint=false, so there is no contradiction.

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?

Three short sentences with the purpose front-loaded, followed by cost and trust notes; nothing is padded. The cost sentence is slightly hedged ('actual cost follows your plan') but still earns its place.

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?

Cost, trust handling, and required parameters are covered, and with no output schema the description responsibly defers return-shape details. However, for a tool with six parameters sitting in a dense family of near-identical seller/market tools, the absence of any placement guidance leaves a real completeness gap.

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 every parameter including the enum marketplace and the compatibility-only newProduct is already documented in the schema. The description adds no format, default, or interaction detail beyond that, which is the expected baseline when the schema carries the load.

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 first sentence names a specific verb and resource: 'Retrieve seller-country distribution for a category,' which clearly states what is produced and its scope. It does not, however, differentiate from close siblings such as amazon_market_seller or amazon_market_seller_type, leaving the agent to guess which seller-related tool fits.

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 when-to-use guidance, no prerequisites, and no naming of alternatives among the many amazon_market_* siblings. The only conditional guidance is financial (cost per call), not selection guidance, so the agent has no signal for choosing this tool over the adjacent seller tools.

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