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

Annotations already declare readOnlyHint=true, and this is plainly a GET, so the safety profile is covered. The description adds the endpoint path and the totals-vs-per-warehouse duality but says nothing about pagination, permissions, or what happens with an unknown productGuid, which is the remaining burden for a read tool.

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?

Two tight sentences: the scope and mode-selection fact comes first, the intent framing and endpoint second. No filler, nothing redundant with the title.

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 four-parameter read with full schema coverage and no output schema, the description conveys mode selection and return shape ('totals, or broken down per warehouse') well. It leaves date-filtering semantics to the schema, which is acceptable here.

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 productGuid, asAtDate, allWarehouses, and warehouseCode are all already documented in the schema, including the 'ignored with allWarehouses' caveat. The description's mention of allWarehouses=true adds emphasis but no information beyond the schema, so the baseline 3 is correct.

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 and resource ('stock on hand for one product') and scopes it to a single product, which distinguishes it from the sibling list_stock_on_hand. It also names the underlying endpoint, so the agent knows exactly what is being fetched.

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?

Gives a clear usage frame ('the direct answer to how many do we have and where?') and explains the allWarehouses toggle that selects between the totals and per-warehouse views. It does not explicitly name list_stock_on_hand as the multi-product alternative or state when not to use this tool, so it falls short of a 5.

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