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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely new context: the data source is NBP, it offers three distinct modes, and gold is addressed through a currency-style code. It does not mention caching, update cadence, or whether history and the current table are returned together, but that is a minor gap given the annotation coverage.

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 dense sentence with no filler, and the three modes are listed up front. It is a grammatical fragment rather than a sentence, which is acceptable in this context but slightly reduces readability.

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 an output schema present, return formatting need not be described, and both parameters are fully specified in the schema. The remaining gap is that 'table' is not qualified (which NBP table) and it does not say what days does when code is omitted; otherwise an agent has enough 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 both parameters are fully documented including the XAU convention and the 'omit for main currencies' rule. The description largely restates the schema (XAU = gold) rather than adding new semantics, so the baseline 3 applies.

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 the specific resources (NBP mid/bid/ask currency rates against PLN, single-currency history, XAU gold price) and the three operating modes, which distinguishes it from siblings like get_bank_rates or get_interest_rates. It is phrased as a noun fragment with no verb, so the 'retrieve' action is implied rather than stated, keeping it just short of a 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?

Usage is only implied through parameters: omit code for the main-currency table, supply a code for history, use XAU for gold. There is no explicit when-to-use versus get_bank_rates (bank vs NBP rates is a real ambiguity an agent cannot resolve from this text) and no stated exclusions or prerequisites.

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