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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds useful operational details beyond annotations: cost per call ($0.005), HTTP method (GET), and data source (ISO 3166). No contradictions with annotations.

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 that communicates the resource, input-to-output mapping, source, cost, and endpoint with no wasted words. The primary purpose is front-loaded in the first three words.

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 one-parameter, read-only lookup with no output schema, the description covers input format, expected return fields, source, and cost. Minor omissions like error behavior or exact response structure are not critical given the tool's simplicity and the parameter-level schema.

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%, with the 'q' parameter fully described and an example provided. The description reinforces input semantics by mentioning 'Name/ISO code' but adds little beyond what the schema already states, so baseline 3 is appropriate.

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?

Description clearly states the tool provides country metadata, mapping a name or ISO code to currency, capital, calling code, languages, and flag. It is distinguishable from sibling lookup tools by naming the country-data domain, though it lacks an explicit action verb like 'look up' or 'retrieve'.

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 description implies usage by defining the resource and output fields, but it does not explicitly state when to use this tool versus alternatives or when not to use it. For a simple, domain-specific lookup, this is adequate but not fully explicit.

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