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

Annotations already declare readOnly/openWorld/idempotent/non-destructive, so the safety profile is covered. The description goes beyond them by disclosing the cost model ('1 credit per call') and the exact response shape, which are not in any structured field. It omits rate limits or error behavior, so not a full 5.

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?

Front-loaded purpose sentence followed by two compact payloads (cost, output shape) with no filler. The inline output structure is dense but earns its place because no output schema exists. Slightly overloaded in a single block.

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 no output schema, stating the return object shape ({type, query, results, count, total, truncated}) is exactly what an agent needs, and the cost disclosure is important for a metered API. Remaining gap is the un-explained 'limit' parameter, but the definition is otherwise sufficient for correct invocation.

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 50%: 'query' and 'country' are documented in the schema, while 'type' and 'limit' are not. The description recovers 'type' by enumerating the four categories and clarifies 'query' as code-or-name-fragment, but says nothing about 'limit' (default 10, max 50) or when 'country' applies. Baseline 3 for partial compensation.

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 ('Look up') and enumerates exactly which standard code sets are covered (ISO 3166 country/subdivision, ISO 4217 currency, ISO 639 language). No sibling tool (currency_rates, timezone_convert, etc.) overlaps this scope, so an agent can route here unambiguously.

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?

The enumeration of covered code systems implicitly tells the agent what this tool is for, but there is no explicit when-to-use/when-not guidance or named alternative for adjacent tasks (e.g. vs currency_rates for rates rather than codes). Usage is inferable but not stated.

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