retrieve_custom_images_stats

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety is covered. The description adds real value beyond that by naming the returned metrics (image count, used/free/total disk space), which matters since no output schema exists. It says nothing about scope (account-wide vs per-region) or permissions, keeping it short of a 5.

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 core sentence is front-loaded and useful, but the description literally restates the same opening clause twice ('List statistics regarding the customer's custom images' appears verbatim in both halves). The second occurrence should have been merged into a single sentence.

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 parameterless read-only stats endpoint with no output schema, the description covers what the tool returns well enough to call it. The remaining gap is scope/preconditions, which is minor here.

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 is one optional parameter (x-trace-id) with 100% schema description coverage, so the schema already explains it. The description adds nothing about it, which is acceptable at full coverage but is the baseline rather than a contribution.

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 verb (List) and resource (statistics for the customer's custom images), and enumerates the metrics returned. It is distinguishable from siblings like retrieve_image_list or retrieve_image, though it never explicitly contrasts itself with them.

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?

Usage is only implied: an agent can infer this is the endpoint for aggregate image storage metrics rather than image records. There is no explicit when-to-use/when-not guidance and no mention of retrieve_image_list as the alternative for listing the images themselves.

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