Amazon break-even and target-margin price

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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and a closed-world scope, so the safety profile is covered. The description adds genuine behavior beyond that: strict input validation that rejects unknown/invalid fields by name rather than silently adjusting, FBA price-band and whole-price referral-band handling, and the fallback to highest reachable margin when the target is impossible.

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?

Front-loaded with the core purpose, then behavior, then inputs. Four dense sentences with little waste, though the trailing validation sentence and the source-URL/calculator mentions run slightly long for what they convey.

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?

An output schema exists, so return values need no prose explanation, and the description still notes key output elements (itemized fees, assumptions, fee-table version/date). For an 18-parameter tool with conditional FBA/FBM requirements, the description covers the complexity and edge cases adequately.

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 18 parameters are documented in the schema itself, giving a baseline of 3. The description adds only generic semantics (FBA vs FBM, price bands) rather than clarifying individual fields, so it neither compensates for a gap nor adds much beyond 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 ('Find the lowest Amazon.com (US) item price that breaks even and the lowest that reaches target_margin_pct'), scopes it (US, FBA or FBM), and implicitly distinguishes itself from the sibling fee/profit tools by being the inverse price solver. An agent can tell it apart from amazon_profit and amazon_fees without opening a schema.

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 explains what it computes and that it shares the fee engine with the free calculators, but never states when to pick this over amazon_profit (known-price) or amazon_fees (fee lookup). Usage context is implied by the tool's nature rather than stated, and no alternatives are named explicitly.

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