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

Annotations already declare readOnly, idempotent, openWorld, and non-destructive, so safety is covered. The description adds genuinely new operational context: 1 credit consumed per request including failures, and the Exchange Rates API key requirement. It stops short of describing the response shape.

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 tight sentences, front-loaded with the core action and immediately followed by cost/key constraints. No filler or repetition of the schema.

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 read-only conversion call with full schema coverage and rich annotations, the description covers cost, auth, and the date/latest-rate choice. With no output schema, it could mention what comes back (converted amount and rate), but this is a minor gap.

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 base, target, date, and base_amount are already documented with patterns and defaults. The description echoes 'base', 'target', 'amount', and 'past date' without adding format, multi-currency, or amount-limit details beyond the schema, so 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?

Names a specific verb (convert) and resource (currency amount) with scope qualifiers: 'from a base currency to one target currency'. It implicitly separates itself from get_exchange_rates/get_historical_rates by converting an amount rather than listing rates, but it never names those siblings 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?

It gives context for the two modes (latest rate vs a past date) and discloses the credit cost and API key requirement, which guides the decision to call. However, it never states when to prefer this over abstractapi_get_exchange_rates or abstractapi_get_historical_rates, so the routing choice is left to inference.

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