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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds substantial behavioral context beyond that: the Sales & Traffic vs. FBA Inventory Health velocity fallback, source attribution, finalization-lag exclusion of not-yet-due dates, and the rule that AWD on-hand is excluded from the numerator. It does not, however, describe pagination or result-shape behavior, so 4 rather than 5.

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?

Purpose is front-loaded in the first clause and the routing instruction is cleanly placed at the end. The middle source-selection sentence is a dense run-on that packs three clauses (fallback, lag exclusion, lookback sizes), which hurts readability slightly but each clause carries real information.

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 an output schema present, the description need not explain return values, and it covers what the schema cannot: data-source provenance, fallback behavior, AWD treatment, sort order, and sibling routing. For a 10-param read-only analytics tool this is a complete briefing.

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 description coverage is 100%, so the schema already documents all 10 parameters (sku, asin, limit, offset, sort_order, filters, lookback). The description reinforces a few semantics (lookback values 7/30/60/90, sort ordering) but adds no syntax or format detail beyond the schema, so the baseline 3 applies.

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 precise verb and resource ('replenishment coverage: days of stock remaining') and even gives the computation (FBA fulfillable + FBA inbound divided by recent FBA sales velocity). It names the sibling tools it is not (get_fba_inventory/get_inventory_health/get_inventory_risk_triage), so an agent can distinguish it without opening schemas.

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?

Contains explicit exclusions ('Do not use for raw stock counts, aged inventory fees, or broad triage') paired with the named alternatives to use instead. It also sets the positive condition (per-ASIN/per-FBA-SKU replenishment coverage). This is textbook when/when-not routing.

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