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

Annotations provide only readOnlyHint=false, so the description carries nearly the full burden and does so: it discloses the destructive scope of 'replace' (wipes and restates every (account, zone) present), the confirmationToken requirement, the 2000-row cap, and the OAuth + OWNER role prerequisite. These are the exact traits an agent needs before invoking a mutation.

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 identity, then workflow, mode semantics, limits and prerequisites in a tight sequence. A couple of clauses restate schema-level details (e.g. the rule multipliers), costing a bit of density but nothing is truly wasted.

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?

With no output schema, the description usefully sketches the preview return (warnings, SKU-grain diff, confirmationToken). It says less about what a successful commit returns, but for a 7-param destructive import the coverage is close to sufficient.

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 already 86%, yet the description still adds real meaning: it explains that zone is a delivery country or 'ROW', that rule controls what cost multiplies ('per_unit'/'per_parcel'/inherit), and spells out the exact upsert key set (asin, sku, zone, period) for merge mode. Some of the rule/period explanation duplicates the schema text.

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?

Opens with a specific verb+resource+scope: 'Import PER-PRODUCT FBM cost overrides for ONE account', and immediately frames the data as 'the exceptions to the rate book', which distinguishes it from the sibling import_fbm_zone_rates without the agent opening either 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?

Clearly states the two-step workflow (preview without commit, then commit with token) and explains exactly when 'merge' vs 'replace' applies, warning that replace is destructive with a partial payload. It doesn't explicitly name import_fbm_zone_rates as the alternative for base zone rates, leaving that routing to inference.

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