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

The readOnlyHint annotation already establishes this as a safe, non-destructive operation. The description adds useful behavioral context beyond that: it is a cheap credential check and returns IDs, codes, location, and per-GB pricing. It does not discuss errors or pagination, but for a simple read-only list this is sufficient.

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 plus a compact endpoint reference. The purpose is front-loaded, the return fields are listed efficiently, and every sentence adds specific value without 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 operation with no output schema, the description supplies enough detail: the resource, returned fields, a credential-check use case, and the underlying API endpoint. An agent can select and invoke it correctly without further context.

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 are no parameter semantics to document. Per the scoring rule, a 0-parameter tool with an empty schema has a baseline of 4; the description correctly avoids unnecessary parameter discussion.

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?

States a specific verb and resource ('List bunny.net's edge regions') and immediately enumerates the returned fields, so the agent knows exactly what this tool does. It is clearly distinct from all sibling tools, which cover DNS, storage, billing, purge, and other resources.

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?

Provides an explicit practical use case: 'A cheap way to confirm the API key works.' This gives clear context for when to call it, though it does not state exclusions or compare against alternatives, which is minor given that no sibling lists regions.

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