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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, and the description adds substantial beyond-annotation context: data sources (World Bank, IMF, BIS, ECB viaEuroArea flag), the Fisher-relation constraint requiring nominal and inflation within a year, the ex-post (not expectation) nature of real rates, and the flat-not-forecast projection caveat.

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 a plain-language framing sentence, then dense, information-bearing detail on sources, computation rules and caveats. Long but nearly every clause carries meaning, so no serious waste.

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?

An output schema exists, so return-shape explanation isn't needed. The description nevertheless covers both invocation modes, source hierarchy, the computation guard, and the drop/ranking semantics — everything an agent needs to call it 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 coverage is 100%, so the baseline is 3. The description adds the ranking universe ('41-country spine') and the important drop policy ('missing a metric lacks the key and is dropped from a ranking, never scored 0'), but the core parameter semantics (codes, ignored params) largely restate 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+resource ('real rates... returns side by side: consumer-price inflation, policy rate, deposit and lending rates') and is unmistakable against siblings like compare_tax_rates or calculate_ppp. An agent knows exactly what this returns without opening the schema.

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?

Explicitly describes the two modes: with `countries` (two or more) it returns side-by-side comparison; omitting `countries` ranks the 41-country spine by one `metric`. It also states that `sort`/`metric` are ignored in comparison mode. No sibling alternative is named, keeping it short of a 5.

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