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

Annotations only declare readOnlyHint=false; the description carries the rest and does it well, disclosing the two-step preview/commit requirement, the OWNER role + OAuth prerequisite, the 2000-row cap, the destructive semantics of 'replace' (rows absent lose their count), and the 0-vs-absent distinction. That is substantial mutation-transparency value beyond the annotations, though it does not describe the diff/warning payload in detail.

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-loads the deprecation notice and the routing instruction, then the semantics. It is dense and somewhat long for a single description, but nearly every clause (coverage ladder position, 0-vs-absent, merge/replace, row cap, role) carries operational weight.

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 mutation tool with no output schema, the description supplies everything an agent needs to call it correctly: prerequisites, two-step flow, mode semantics, row limits, and the absent-vs-zero interpretation. Nothing critical is left for the agent to infer.

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 83%, so the schema already documents most parameters (mode, asOf, region, quantity, commit, confirmationToken, reason, account). The description reinforces mode semantics and the preview/commit token flow, and clarifies that '0 is a real count, absent means unknown', but this largely duplicates the schema text rather than adding new syntax or constraint detail. Baseline 3 is appropriate given the high coverage.

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 (import) and resource (external stock of ONE account, units held outside Amazon per product × region) and positions it precisely within the product's data model (externalStock, coverageWithExternal). It explicitly distinguishes itself from import_supply_chain as the deprecated predecessor, so an agent can pick the right tool without opening the 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?

Explicitly says the tool is DEPRECATED and to prefer import_supply_chain for new callers, then gives the remaining use case. It also prescribes the mandatory workflow (preview without commit, show user, then commit with token) and spells out when 'merge' vs 'replace' applies.

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