exchange_rates

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is fully covered. The description adds two genuinely useful facts beyond them, the authoritative source and the rate direction (RUB per 1 unit), but says nothing about the validity period of Central Bank rates or whether a non-trading day falls back to a prior quote.

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?

A single front-loaded sentence with the source, the unit convention and the use case packed into it; nothing is redundant and nothing needs reordering.

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?

For a two-parameter read-only lookup with full annotation coverage and no output schema, the definition is nearly sufficient, and 'RUB per 1 unit' usefully implies the return shape. It stops short of noting that quotes are date-stamped by the Central Bank and may not exist for arbitrary dates, which an agent calling with a weekend date would want to know.

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%: on_date documents the YYYY-MM-DD format and today default, and currencies documents the code list plus the all-if-omitted behavior. The description adds no parameter meaning beyond that, which is the correct baseline when the schema does the work.

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 names a specific resource (official Bank of Russia exchange rates), states the unit convention (RUB per 1 unit), and gives the business context (customs payments). It is distinguishable from every sibling, none of which is a rate lookup, though it never states the retrieval verb or scope explicitly.

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?

'used for customs payments' implies the context in which an agent would reach for this tool, but there is no explicit when-to-use rule, no mention of when a different tool (e.g. calc_import_payments, which presumably consumes these rates) is the better choice, and no exclusions.

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