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

Adds context beyond the readOnly/openWorld annotations: price per successful call, payment rails, the fact that failed calls are free, and that results are the latest year(s) in the source. It does not cover rate limits, auth flow details, or data staleness.

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?

A tight paragraph with the resource, default, caveat, and pricing front-loaded. No wasted sentences, though the payment clause sits mid-paragraph rather than trailing.

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?

Covers defaults, source limitations, and the paid-call model; an output schema exists so return-shape explanation is unnecessary. Missing only explicit sibling routing and error behavior, which are minor for a read-only stats 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 coverage is 100%, so the baseline is 3. The description adds meaning for the default indicator (CO2 emissions by fuel and product, MtCO2) and echoes the latest-years behavior, but doesn't add syntax or constraints beyond the schema.

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: IEA energy statistics for one country and one indicator, with the default indicator spelled out. It distinguishes itself from other energy data siblings by naming the source (IEA stats API), but doesn't explicitly route against them.

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 one-country/one-indicator scope and the 'not every indicator has data for every country' caveat imply when the tool applies. There is no explicit when-to-use or when-to-prefer-a-sibling guidance, even though roughly 50 energy siblings exist.

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