list_regions

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

No annotations exist, so the description carries the full disclosure burden; it covers filter behavior and the mapping result, which is the core behavior. It says nothing about authentication requirements, whether the region set is static or dynamic, or the concrete return shape (map vs. list of pairs). Adequate but with clear gaps for an unannotated tool.

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 very short sentences, front-loaded with the return mapping before the filter detail and the negative hint. Nothing is padded, though the closing clause 'there is nothing to resolve here' is slightly oblique in phrasing.

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?

The tool has one optional param, no output schema, and no annotations, so the description must supply output shape and argument format. It gives the conceptual output (ids to display names) and filter behavior, but leaves the valid `service` value space and the exact return structure implicit.

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 coverage is 0% — the single `service` param has only a type and default, no description. The description compensates by explaining the filter semantics for `service`, but never says what form the value takes (a service id from list_services, a display name, etc.), which is the main ambiguity an agent faces.

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 resource and output semantics ('Region ids -> display names'), which is precise about what the tool returns. It does not name or differentiate itself from the nearest sibling (compare_regions), so it stops short of a 5.

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 conditional: with `service`, only regions where it is sold are returned. It also supplies a rare and valuable negative hint — that other tools accept friendly names directly, so there is nothing to resolve here — telling the agent when not to call it. No sibling tool is named as the alternative for region comparison, so not a 5.

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