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

Annotations already establish read-only and open-world behavior, while the description adds meaningful operational context: the exact data source, the fact that the route name is retained for the owner, and x402 payment terms including charges only for successful calls. It does not describe return formatting, but an output schema exists, so the added behavioral value is solid.

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 front-loaded with the core purpose and then adds the benchmark caveat, history scope, and payment terms. Every part is relevant, though the owner-route-name note is slightly less essential than the rest.

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 one-parameter read-only reference-price tool, the description supplies source, frequency, unit, historical range, benchmark caveat, and payment model. With annotations and an output schema also present, an agent has enough context to call this tool correctly.

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%, and the single months parameter is already documented as 1 to 24 with default 3. The description's mention of latest value plus up to 24 months of history reinforces but does not materially extend the schema semantics.

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 names the specific resource, frequency, unit, currency, and source series: monthly iron ore reference price in USD per dry metric ton from World Bank PIORECRUSDM via FRED. It also explicitly distinguishes this from the Platts 62% Fe CFR Qingdao spot benchmark, so an agent can tell what data it actually returns.

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?

It clarifies that this is a World Bank monthly reference series rather than the Platts spot benchmark, which is useful selection guidance. However, it does not explicitly state when an agent should choose this tool over related commodity or steel tools, so the usage guidance is strong but not fully explicit.

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