List regions

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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is fully covered structurally. The description adds only the discovery-before-mutation context; it says nothing about whether the region list is static or dynamic, cached, or how it relates to existing deployed services.

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?

A single sentence, front-loaded with the usage trigger ('Use this when...') and ending with the concrete downstream actions. Nothing extraneous.

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 no-parameter, read-only discovery tool with rich annotations and no output schema, the description covers the essential purpose and timing. The one remaining gap is that it doesn't hint at the return contents (region identifiers), which matters because no output schema exists to document them.

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 takes zero parameters, so there is nothing for the description to disambiguate; baseline applies. No misleading parameter language is present.

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 makes clear this returns the set of available deployment regions, which is a specific verb+resource rather than a restatement of the name. It doesn't explicitly state the shape of what comes back (names vs. slugs), so it falls short of a 5, but an agent can distinguish it from siblings like service_list or template_list without opening a schema.

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 gives an explicit trigger — call this before creating a service or addon — which ties the tool to concrete downstream siblings. There is no explicit exclusion or statement about when it's unnecessary (it is safe and idempotent, so it could be called freely), leaving that to inference.

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