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

Even though annotations already declare readOnlyHint and destructiveHint, the description adds significant behavioral context: it reports what columns were missing, accepts aliases for demand history, notes that only sku is required, and explains how on_order prevents rebuying. This goes far beyond the annotations and enriches the agent's understanding.

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?

Every sentence earns its place. The description is front-loaded with the core function, then inputs, outputs, usage triggers, prohibitions, required fields, a specific caveat about on_order, and size limits. It is dense but not bloated, with no filler.

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 complex tool with 20 parameters and an output schema, the description covers the essential context: what to send, what not to do, output contents, size constraints, and how to avoid common errors like buying in-transit stock. The presence of an output schema means return-value details need not be repeated, and the description fills all other gaps.

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?

The description adds meaning beyond the schema by explaining the core inputs ('Send a stock list (and sales history if there is one)'), the necessity of on_order, and the flexibility of column names. It doesn't document every one of the 20 parameters, but the schema itself covers some, and the description orients the agent on the critical semantics without redundancy.

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?

Description starts with a specific verb+resource: 'Works out what a business should buy, how much, and when.' It clearly enumerates the outputs (order quantities, reorder points, overstock, cash stuck, buying list) and differentiates from the sibling by stating size limits and pointing to inventory_optimizer_get_engine for larger datasets.

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?

Provides explicit and strong guidance: 'ALWAYS call this whenever stock, ordering, reordering, overstock or running out comes up, even for a single product. Do not work the number out yourself.' It also tells the agent never to refuse due to missing columns, to include on_order to avoid duplicate recommendations, and gives clear size thresholds with an alternative for larger data.

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