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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive. The description adds value by disclosing the returned data fields (ISO3 codes, region, HDI band) and the purpose of canonical spellings, which informs the agent about the tool's output without contradicting annotations. It doesn't mention any quirks like case sensitivity, but the annotations cover safety, so this is adequate.

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, both purposeful. The first declares the action and output, the second gives the usage context. No redundancy or filler, and the essential information is front-loaded.

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 simple lookup tool with one optional parameter, no output schema, and comprehensive annotations, the description provides everything needed to call it correctly: what it returns, why to use it, and how to use the query. Nothing essential 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?

The schema covers 100% of the parameter with a clear description ('Name fragment or ISO3 code. Omit to list all.'). The description itself adds no new parameter details, only a usage hint. With full schema coverage, a baseline of 3 is appropriate, and the description doesn't need to compensate further.

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 states a specific verb ('List or search') and resource ('countries and territories GLOBOCAN publishes cancer estimates for'), and details the returned attributes (ISO3 codes, world region, HDI band). It also distinguishes from sibling tools like globocan_cancer_in_country by focusing on the country vocabulary, not cancer data.

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?

'Call this to find the exact country spelling the other tools expect' explicitly tells the agent when to invoke this tool—as a lookup before using other GLOBOCAN tools. It implies the alternative is directly using the other tools with potentially wrong spellings, making the usage context clear.

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