list-regions

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

The annotations already declare readOnlyHint=true and openWorldHint=true, so the description adds extra context by giving example region codes and noting their role as inputs to other tools. This goes beyond the annotations in a useful way, though it doesn't describe return format or error behavior.

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: the first states the function with examples, the second gives usage context and directive. No fluff, fully 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?

Given zero parameters, rich annotations (readOnlyHint, openWorldHint), and a simple list-only purpose, the description is complete. It even anticipates the user's next step by noting dependent tools.

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, so the baseline is 4. The description doesn't add parameter-specific info because none exist, but it does clarify that the output (region codes) will be used as inputs elsewhere, adding context to the tool's role.

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 'List all available market region codes' with specific resource and action. It provides concrete examples (e.g., 'eudm', 'usdm') and distinguishes itself from sibling list-* tools by focusing on regions as a distinct entity.

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?

Explicitly states that region codes are required inputs for list-makes, search-by-model, and wheel-upsteps, and advises to 'Start here when region is unknown.' This gives clear when-to-use guidance and even names dependent tools.

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