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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, covering safety. The description adds that it returns codes and human-readable titles, and notes no auth and unlimited free access. This provides behavioral context beyond the structured fields without contradicting them.

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 sentences, zero fluff, with the core purpose and examples front-loaded. The response format and access model are stated efficiently. Every sentence earns its place.

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?

Output schema exists, so return format is covered. The description includes usage context, examples, and access details. For a listing/discovery tool, this is complete; missing details like error handling or pagination are minor and not required 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 description coverage is 100%, so the schema already documents all parameters. The description adds the world bank income group example not present in the schema, but otherwise repeats schema content. Baseline 3 is appropriate given full coverage, with a slight bonus for the extra example.

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 clearly states the tool lists valid values for a WHO GHO dimension, provides concrete examples (COUNTRY, REGION, SEX, AGEGROUP, WORLDBANKINCOMEGROUP), and distinguishes it from data-querying siblings by emphasizing discovery of filter values before querying indicator data. This is a specific verb+resource with clear scope.

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 explicitly frames the tool as a prerequisite step ('Essential for discovering valid filter values before querying indicator data'), which tells the agent when to use it. It does not explicitly name alternatives or exclusions, but the sibling tools (who.health.data, who.health.indicators) are clearly for data queries, so the guidance is implicit and adequate.

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