List Regions

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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds the context that this is a controlled vocabulary with examples, but doesn't disclose further behavioral details like pagination or return format. This is acceptable given the annotations and simplicity, but not rich.

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?

The description is a single, well-structured sentence that front-loads the action and includes examples. Every word earns its place with no redundancy or filler.

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 zero-parameter, read-only list tool, the description is completely adequate. It explains what the tool returns (a list of region codes) and provides examples, without needing to explain return values or side effects. No output schema exists, but the description covers the key information.

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 tool has zero parameters, and schema coverage is 100% (nothing to document). The description explicitly notes 'no parameters' in the schema and doesn't need to add parameter details. Baseline for 0 params is 4, and no additional explanation is necessary.

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 a controlled region vocabulary for the provider registry, with concrete examples ('us', 'eu', 'uk', 'global'). The verb 'List' and resource are specific, and it distinguishes itself from sibling tools focused on providers or queries.

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 context by noting the vocabulary is 'used by the provider registry', making it clear this is a reference for valid region values. It doesn't explicitly mention alternatives or exclusions, but for a simple list tool, this is adequate.

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