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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description adds real behavioral context beyond the annotations: the size of the result set (462 units) and the important scope constraint that these codes apply only to uis_get_data, not other statistical servers.

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?

Two sentences with no filler, and the most important facts — what the codes are and where they apply — are front-loaded. Every clause carries information an agent needs.

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 an output schema present, the return format needn't be explained, and the description still clarifies that no statistical values are returned. For a low-complexity lookup tool with full parameter documentation and annotations, nothing an agent needs to call it correctly is missing.

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%, so all five parameters (type, limit, offset, search, provenance_mode) are already documented, including the NATIONAL/REGIONAL enum and the search-by-name-or-code semantics. The description's 'Filter by name/code and type' merely restates what the schema provides, 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?

The description names the specific resource (462 UNESCO UIS geographic codes) and its exact role: supplying valid codes for uis_get_data. It distinguishes its output from statistical data and explicitly scopes the codes to uis_get_data rather than other statistical servers, so the agent can separate it from siblings like uis_get_data and uis_search_indicators.

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 clearly frames the use case — resolving valid geographic codes before calling uis_get_data — and states what the tool does not do (return statistical values). It stops short of an explicit 'call this first to resolve codes' instruction or direct comparison with siblings, but the context is unambiguous.

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