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 genuinely useful operational detail absent from annotations: five sections are returned by default, and "all" yields roughly 35 KB — a practical payload-size warning. It does not discuss error behavior for unknown country codes.

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 paragraph that front-loads the resource and content scope, then moves to usage examples and defaults. The long content enumeration is justified because it tells the agent what questions this tool can answer, though it borders on a feature dump.

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, the description carries the burden of explaining return shape and does so at the section level, plus defaults and approximate size. An agent can call it correctly on the first try; only the section-name vocabulary for non-default requests is left to the 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%, so both parameters are already documented in structured fields, including the accepted name/ISO/gec code forms. The description largely restates the accepted input formats, adding only the size note for "all", which places it at the baseline for full schema coverage.

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 resource (CIA World Factbook country profile) and enumerates the substantive content it returns, so an agent knows exactly what data it gets. It never names the sibling tools it is distinct from (factbook_compare, factbook_entities, factbook_fields), leaving that differentiation to inference from the tool name.

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?

Provides concrete trigger phrasings ("tell me about Kenya", "what type of government does Chile have") that map user intent to this tool, and explains the default-vs-sections behavior. It stops short of stating exclusions or pointing to alternatives such as factbook_compare for multi-country questions.

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