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

Annotations already declare read-only/idempotent/open-world, and the description adds substantial extra behavior: a max 5-minute cache with a displayed query time, the rule that source failure or a missing reference date is NOT treated as 'no change', the caveat that no_new_period does not prove an unchanged same-date value, and an explicit statement that it does not subscribe, reserve, or store personal work.

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?

The core function and parameter defaults are front-loaded, followed by workflow and caveat sentences. It is dense and every clause carries information (defaults, first-call fallback, caching, negative-result semantics), though a couple of fragments such as '/day는 미확인' assume context the agent may not have.

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 covers return content (amount + difference) and hints at output fields (nextCheck.arguments, no_new_period, query time). Failure/missing-reference handling and period coverage limits are disclosed, so an agent can call it correctly. Minor gaps remain around the exact response shape and pagination-like limits.

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 param burden. It explains teu (1-4 entries, default 1700/2500) and since (YYYY-MM-DD), plus the non-obvious semantic that an omitted since on the first call falls back to the prior public date. The only gap is the cryptic '/day' reference, which is not tied to either parameter.

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?

It states a concrete verb+resource: read the official public table and return the latest US$ amount for the selected teu plus the difference versus a since date. The scope is further narrowed (only periods still in the public table, HARPEX Index vs linear amounts are separate), so an agent knows exactly what it gets. It does not name or contrast any sibling tool, which keeps it at 4 rather than 5.

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?

Clear usage context is given: on the first call omit since to compare against the previous public date, and persist nextCheck.arguments for later checks. It also implicitly says when NOT to expect results (periods no longer in the table). No explicit alternatives/exclusions are named, but the sibling set is unrelated, so this is sufficient.

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