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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds value beyond that by disclosing data provenance (The Economist big-mac-data, MIT), the temporal bounds of the dataset (since 2000), and the default release behaviour.

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?

Front-loaded with the resource identity, then scope, then fallback behaviours, then provenance. Dense but every clause carries information; no filler or marketing language. Slightly long as a single opening sentence, but not padded.

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?

No output schema exists, and the description compensates by enumerating the returned measures and the comparison currency basket (USD, EUR, GBP, JPY, CNY), which the schema does not mention. With four optional parameters all documented in the schema and rich annotations, the remaining gap is only the absence of an explicit tie-break against big_mac_valuation.

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 date, limit, country and history are already fully documented with formats, defaults and resolution rules — this is the baseline 3 case. The description's only extra parameter-adjacent content is restating the omit-country behaviour and the history-since-2000 semantics, which the schema already carries.

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+resource (retrieve The Economist Big Mac index for a country) and enumerates exactly what is returned: local price, dollar exchange rate, dollar price, and raw/GDP-adjusted over- and under-valuation. However, it never distinguishes itself from the closely related sibling big_mac_valuation, which an agent will almost certainly have to choose between.

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 description gives real usage context for parameters (omit country to list every country in one release; use history for the full series since 2000), which implies how to shape a call. But it offers no when-to-use/when-not guidance and no routing to alternatives, which matters given the near-identical sibling big_mac_valuation.

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