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

Annotations already declare read-only, non-destructive, non-idempotent behavior, so the bar is lower, and the description still adds real value: the per-call credit cost, the warning that repeated calls may charge again (consistent with idempotentHint=false), and a prompt-injection caveat to treat returned data as untrusted. It stops short of describing what a 'concentration' measurement returns, which is the remaining behavioral gap.

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 purpose is front-loaded in the first sentence, followed by compact cost and safety notes. The two cost sentences overlap slightly ('default cost' vs 'actual cost follows your plan' vs 'repeated calls may charge again'), but overall it is tight and readable.

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?

This is a 6-parameter measurement tool with no output schema, so the description arguably should describe the shape of the returned concentration data, and it does not. Inputs are fully covered by the schema and the cost/safety notes are present, making it adequate but incomplete on the output side.

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 all six parameters, including the enum marketplace and format hints, are already documented in the schema. The description adds no parameter-level meaning beyond that, so the baseline of 3 applies.

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: 'Measure seller concentration within an Amazon category.' That is concrete and actionable. It does not, however, distinguish itself from close siblings like amazon_market_seller_location or amazon_market_seller_type, so sibling differentiation is missing.

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 stated prerequisites, and no named alternative among the many amazon_market_* siblings. The only contextual information is about billing, not about choosing this tool over another.

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