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

Annotations already carry readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavior beyond those: the 1-credit cost, the extra credit for a_plus_content, the exclusive-OR constraint between identifier and url, and the instruction to set a_plus_content only on explicit user request. It does not disclose error/not-found behavior, but the cost and constraint disclosures are genuine value beyond the annotations.

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 paragraphs with a clear progression: what it returns, when it is the primary choice, when to choose alternatives, and input/cost constraints. The verb+resource is front-loaded and every sentence earns its place. The 13-item field enumeration is long but justified since no output schema exists to document the response; it is slightly more verbose than strictly necessary, stopping short of perfect economy.

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?

For a complex 7-parameter tool with 0 required parameters and no output schema, the description covers the response surface via the field list, identification constraints, cost, and marketplace routing. The main gaps are error behavior for invalid ASINs or URLs and explicit acknowledgment of the open-world scope implied by openWorldHint, but nothing an agent needs to invoke the tool correctly is missing.

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% (all 7 parameters have descriptions), so the baseline is 3. The description adds two things the schema does not express: the mutual-exclusion rule ('Provide EITHER the identifier field OR url — never both') and the cost consequence of a_plus_content. Those additions justify a 4, though the description appropriately leaves per-parameter syntax to the schema.

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+resource ('Fetch complete, structured information about a single Amazon product') and enumerates 13 concrete data fields (title, brand, images, Buy Box price, Prime eligibility, Best Sellers Rank, variants, top reviews, etc.), making the return surface unmistakable. It explicitly differentiates itself from siblings by declaring 'the primary tool for product analysis, listing enrichment, and price monitoring' and naming get_product_offers, get_bestseller_rank, and get_package_dimensions as more targeted alternatives.

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 an explicit selection rule ('Use this tool when you need a full product profile') followed by three named alternatives with their conditions: get_product_offers for competing seller prices (notably flagged as cheaper context), get_bestseller_rank for sales rank, and get_package_dimensions for shipping dimensions or FBA fee category. This is exactly the when/when-not/alternatives guidance the dimension asks for.

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