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

Annotations already declare readOnly, idempotent, non-destructive, closed-world access. The description adds real behavioral context beyond that: data is cached, gaps are not filled, return values carry native units, provenance and age, and China series are revision-aware with daily fixings and licensed gaps kept distinct. It stops short of noting any rate limits or freshness caveats, so it is useful but not exhaustive.

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 core action and the when-to-use routing before the supporting detail, and every sentence carries content. It is slightly dense with domain jargon ('owner-accepted Palimpsest China annual economic series') 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?

With an output schema present, the description need not explain return values, and it correctly explains where the china_series identifier comes from ('the response's china.series catalog') and that providers list their supported currencies. Coverage of the closed-world, no-scoring boundary makes it complete enough for a zero-required-param query 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 description coverage is 100%, so base, quote, days, provider and china_series are all documented in the schema (including the calendar-day-not-count semantics of days and the cn.wdi.* constraint on china_series). The description repeats the general intent of these params but adds no new syntax, defaults, or format 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?

The description names a specific verb (query), resources (dated FX observations plus optional accepted China annual series), and the exact output modes (time series, same-date FX cross, observed-interval change). It also carves out scope against siblings, so an agent can distinguish this from world_markets_context and money_market_context without reading either 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?

Explicit selection guidance: 'Choose this for a time series, same-date FX cross, or observed-interval change; use world_markets_context for a chartless overview and money_market_context for funding-desk metrics.' Both the trigger and the two alternatives are named, plus a negative scope list (no collection, model fitting, executable quotes or scoring).

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