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

Annotations already declare readOnlyHint, destructiveHint, idempotentHint, and openWorldHint. The description adds genuinely new context beyond those fields: per-call credit cost, the fact that repeated calls may charge again, and a warning to treat returned data as untrusted. This is meaningful operational context not present in structured fields.

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?

Four short sentences with the core purpose front-loaded, followed by cost and trust caveats. No wasted prose, though the cost sentence and the re-charge sentence could be merged.

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 would ideally hint at what is returned, yet it only mentions 'returned data' abstractly and never describes the response shape or how returnFields affects it. Cost and trust context are covered, but the return-value gap leaves it only partially complete.

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 100%, so all six parameters, including the enum marketplace and the compatibility note on newProduct, are already documented in the schema. The description adds no parameter-level meaning beyond that. Baseline 3 applies 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?

States a specific verb and resource: measuring brand concentration within an Amazon category. This is clearly distinguishable from sibling market tools like amazon_market_seller or amazon_market_goods. It does not explicitly name a sibling to differentiate against, but the task is unique enough to be identified.

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?

The description says what the tool does but gives no guidance on when to use it versus alternatives, no prerequisites, and no exclusions. The agent must infer usage from the name and schema alone.

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