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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered; the description goes well beyond that with the rate source, the non-business-day fallback, the RUB-based cross-rate path, and an explicit rejection rule for future dates. It also discloses the return payload (rate and result rounded to 2 decimals), which is exactly the kind of behavioral detail annotations cannot express.

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 sentences, front-loaded with the action and rate source, then a compact second sentence handling edge cases and the return shape. Every clause carries information — the fallback, cross-rate path, rejection rule, and rounding all matter to a caller.

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 takes on the burden of describing the return values (rate as units of to per 1 from, result rounded to 2 decimals), and it covers the tricky behavioral edges an agent would otherwise have to discover by trial. Nothing needed to call or interpret this tool is missing.

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% and documents all four parameters, including the date default ('defaults to today in the company's time zone'), so the baseline is 3. The description clarifies the direction convention ('units of to per 1 from'), which helps interpret amount/from/to, but adds no syntax, format, or validation detail for the parameters themselves.

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 gives a precise verb+resource ('Converts an amount between RUB, USD, EUR and CNY') and immediately pins down the scope: the Bank of Russia rate, the supported currency set, and the date basis. No sibling tool in the list does currency conversion, so there is no ambiguity to resolve and the purpose is fully self-contained.

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?

It supplies concrete usage conditions rather than leaving them to inference: non-business days fall back to the last business day's rate, cross rates route through RUB, and dates beyond tomorrow are rejected. It does not name alternatives or a 'when not to use', but no plausible alternative tool exists in this toolset, so the omission is minor.

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