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

Annotations already declare readOnly/idempotent/non-destructive, so the safety bar is covered. The description adds real context that annotations cannot: freshness (published each working day after 13:00), unit basis (lei per unit), and output locale (Romanian) — all relevant to interpreting results.

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 compact sentences with no filler. The most decision-relevant facts (what the rates are, their unit, and the default currency set) are 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 and one optional parameter, the description covers what is returned (reference rates in lei per unit), in what language, and how fresh the data is. It stops short of describing the response shape or whether a publication date is included, which would fully close the loop.

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, but the description adds a default currency list (EUR, USD, GBP, CHF, HUF, MDL) that the schema does not document — the schema only describes ISO code format and max 40 items. This is genuine added meaning about default behavior.

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 resource (National Bank of Romania reference exchange rates) with unit semantics ('lei per unit') and publication timing. Siblings (credite, dobanzi_depozite, subiectele_zilei) are unrelated topics, so no sibling differentiation is needed.

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?

Gives clear context for use: daily reference rates published after 13:00, with an explicit default currency set so the agent knows it can call with no arguments. No explicit when-not-to-use or named alternatives, but none are meaningfully available for this data-retrieval tool.

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