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

Annotations already declare readOnlyHint and openWorldHint, but the description adds material behavior they do not cover: a per-call price ($0.005 USDC via x402 on Base) and the fact that results are official values tagged with series id, date and source. Payment terms are exactly the kind of context annotations cannot express. No rate limits, retry or failure behavior, hence not a 5.

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?

Two dense sentences, each clause load-bearing: coverage and sources first, then input-language flexibility, then return shape, then price. No filler and the most important scoping information is front-loaded.

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 no output schema, the description correctly states what comes back (official values with series id, date, source), which is normally the missing piece. Coverage, sources, input modality and payment are all present; only edge cases such as unavailable series, date defaults or partial-day data are unaddressed.

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 0%, so the description carries the burden for both parameters. It gives real semantics — 'question' is a natural-language query in English or Korean, and 'date' scopes the result to a reference date — but omits date format, whether date is optional or defaults to today, and how the question is parsed. Partial compensation for a total coverage gap.

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?

Names a specific resource (Korean rates and FX) and enumerates exactly what is covered: BOK base rate, KOFR, CD, CP, KTB yields 1y-50y, and won FX from named sources (ECOS, KEXIM, customs). This cleanly distinguishes it from the narrower sibling kr_fx_rate, which covers FX only.

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?

Usage is implied rather than stated: the agent can infer this is the tool for Korean rates/FX questions and that kr_fx_rate is the narrower alternative, but the description never explicitly sets a when-to-use or when-not boundary, nor gives prerequisites. Adequate but leaves routing to inference.

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