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

Annotations already declare readOnlyHint/openWorldHint, so the description's added value is meaningful: it names the data source (public product page), the data boundary (no stock or shipping), and a full billing model (USDC per successful call, x402 on Base/Solana/Arc, failed calls uncharged). Cost and failure-charging behavior are exactly the kind of context an agent can't infer from structured fields.

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 sentences, front-loaded with what the tool returns, followed by scope limits and cost. No filler or repeated fields.

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 single-parameter read tool with an output schema and annotations present, nothing essential is missing: source, return fields, scope limits, and pricing are all covered, so an agent can call it correctly and understand the cost.

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 100% and the schema already documents the item format ("letter, optional dash, digits") with the same S-4119 example. The description merely restates that example, adding no syntax or edge-case 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 specific retrieval verb, the exact resource (Uline product by item number), and enumerates what is returned (description, category, unit price). The example item number and the Uline-specific scope make it trivially distinguishable from the many other retailer sibling tools.

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 item-number lookup context is clear and the example anchors usage. It also gives an implicit exclusion ("no stock or shipping data"), telling the agent not to reach for it for inventory questions, but it does not explicitly route to an alternative or state prerequisites.

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