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

Annotations only carry readOnlyHint=true, but the description adds the rate source (Bank of Russia), holiday/weekend fallback behavior, cross-rate routing via RUB, and an explicit error condition (future dates rejected). That is rich behavioral disclosure well beyond the annotations.

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?

Core purpose is front-loaded in the first clause, edge-case rules follow, and the return contract is stated last. No filler; every clause conveys a distinct rule or behavior.

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?

There is no output schema, so the description compensates by documenting the return shape (rate and result, with result rounded to 2 decimals). Combined with the date and error rules, an agent has everything needed to call it correctly.

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 baseline is 3, but the description adds real meaning: it defines rate as 'units of to per 1 from', removing ambiguity about rate direction, and reinforces the date fallback rule that the schema only alludes to. The 'from'/'to' enums are already in the schema.

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 verb (converts) and resource (an amount between RUB, USD, EUR, CNY) with the exact rate source. It is instantly distinguishable from every sibling tool, none of which touch currency.

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 concrete operating context: which currency set is supported, that non-business days fall back to the last business day, that cross rates route via RUB, and that dates after tomorrow are rejected. No sibling overlaps so no alternative needs naming, but it stops short of an explicit 'use this when...' framing.

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