Get Per-Fulfillment-Center Inventory Distribution for an ASIN

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

Annotations already include readOnlyHint=true, and the description adds context about the return payload (totalSellableUnits, distribution array with fields) and the `lastUpdatedAt` null condition. This goes beyond the annotation by explaining output semantics and edge cases, though it doesn't discuss pagination or rate limits, which are not relevant for a small read operation.

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?

The description is a single, well-structured paragraph of moderate length. It front-loads the when-to-use trigger, then states requirements and output. Every sentence earns its place, with no redundant or vague phrasing.

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?

Given there is no output schema, the description explains the return structure (distribution array with fc, state, availableStock, availableStockPercentage) and the nullability of lastUpdatedAt. It also mentions prerequisites for sellerId, making the tool self-sufficient for a user to invoke correctly. This is complete for a simple read-only inventory distribution tool.

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 fully documents all three required parameters (asin, sellerId, marketplace) including patterns and enums. The description repeats the parameter names but adds no new meaning beyond what the schema already provides, so baseline 3 is appropriate.

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?

The description clearly states the tool's function with specific verb+resource: 'get inventory distribution' per ASIN. It explicitly distinguishes from siblings by focusing on inventory levels and fulfillment center stock, which no sibling covers. The trigger phrases ('asks about inventory levels, stock by fulfillment center') make the purpose unambiguous.

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 provides explicit when-to-use guidance: 'Use this when the user asks about inventory levels...' It also lists required input sources (sellerId from list_seller_profiles or Connections page). However, it doesn't mention when not to use this tool or suggest alternatives, so it misses the 'when-not/alternatives' element for a 5.

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