List external storages

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds the contextual detail that storages are 'configured' and 'used as CDN origins,' which is helpful but does not disclose any additional behavioral aspects such as return format, pagination, or limitations. This meets the lowered bar but does not exceed it.

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 sentence that is concise, front-loaded with the verb and resource, and contains no extraneous information. Every word adds value.

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 the tool's simplicity (0 parameters, no output schema), the description is complete. It clearly identifies what the tool returns (configured external storages) and their purpose (CDN origins), which is sufficient for an agent to invoke correctly. Annotations cover the read-only behavior.

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?

There are no parameters, and the schema coverage is 100%. According to the rubric, 0 parameters merits a baseline of 4. The description does not need to explain parameters, and no additional parameter semantics are required.

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 configured external (S3-compatible) storages used as CDN origins, specifying both the verb (list) and the resource (external storages). This distinguishes it from sibling tools like list_buckets or get_external_storage by clarifying the scope (external S3-compatible, CDN origins).

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 establishes clear usage context by specifying the type of storages (external S3-compatible CDN origins), which helps the agent decide when to use this tool versus listing internal buckets or retrieving a single storage. It does not explicitly mention alternatives or exclusions, but the context is strong enough for most cases.

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