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

No annotations exist, so the description carries the full burden and largely meets it: it discloses the return shape (title, unit, frequency, observations, latest, source attribution), the 10-year max span and 3-year default, and the $0.002 x402 payment path. It omits failure modes and rate limits, but the operation is a simple read and the cost/transport detail is unusually explicit.

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?

Dense and front-loaded: a when-to-use clause, then Input, Output, Data, Example, and Price in labeled segments. The chained parenthetical series list is compact but slightly hard to scan; a minor nit about a tight, well-organized definition.

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 only three parameters, no output schema, and no annotations, the description still covers inputs, output structure, data provenance, span limits, an example call, and pricing — enough to invoke correctly. A note on error behavior or empty-result handling is the only meaningful gap.

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?

The schema's 'series' property merely says 'see enum' while the schema actually contains no enum values, so the description's enumeration of all ten series ids supplies essential, otherwise-missing parameter semantics. It also clarifies that start/end are years with a max 10-year span and 3-year default, adding constraints beyond the terse schema descriptions.

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 title and description name a precise resource (US macro time series from BLS and US Treasury) and enumerate all ten supported series ids, so an agent knows exactly what data it can fetch. It also explicitly positions itself against the sibling kr_bok_ecos_series ('pairs with Korea's Bank of Korea series'), which is the main confusable tool.

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?

'Use when you need a US macro time series' gives a clear triggering condition and the Korea pairing hints at the country-scoped alternative. It stops short of stating exclusions (e.g. that this tool cannot return Korean data or non-listed series), so it is strong context without full when-not routing.

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