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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so the safety profile is covered. The description adds real behavioral context beyond that: the list is a today-only snapshot, absent codes may still have history, and nbgQuantity explains the quoting unit (with a concrete JPY example) that would otherwise be misinterpreted as a raw price.

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?

Three sentences, each carrying distinct load: scope, historical caveat, and unit semantics plus alternative routing. The scoping statement is front-loaded and there is no filler.

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?

An output schema exists, so return values need no prose explanation, and the annotations cover the safety profile. What remains — the today-only scope, the historical-gap caveat, and the quoting-unit semantics — is exactly what the description supplies.

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 the single language parameter is fully documented in the schema, including the en/ka enum and the default. The description adds nothing about the parameter, so the baseline of 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?

States a specific verb and resource ('Lists every currency NBG publishes a GEL rate for today') and scopes it to today's published set. It explicitly routes rate retrieval to the sibling nbg_get_rates, so an agent can distinguish it from nbg_get_rates without opening either schema.

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 explicit routing: 'for the rates themselves call nbg_get_rates', which names the alternative and the condition that selects it. It also warns that a missing code may still have historical rates, preventing a false negative when the agent is deciding between this tool and nbg_rate_history.

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