image_disk_usage

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

Annotations already declare readOnlyHint=true, so the safety profile is covered, and the description reinforces it with a [READ] marker. It adds the concrete return fields (total, shared, reclaimable), but says nothing about permissions, target resolution failure modes, or rate/refresh behavior.

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 compact segments: a one-line purpose with return fields, then a single Args entry. Fully front-loaded with zero 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?

With no output schema, the description usefully names the returned metrics (total, shared, reclaimable) and documents the lone optional parameter's default. For a simple read-only single-parameter tool this is nearly sufficient, missing only target resolution 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?

Schema description coverage is 0%, so the description must carry the single parameter, and it does: 'target' is a name from config and omitting it falls back to the default. That default behavior is meaningful semantics not present in the schema, though it does not say what valid target names look like.

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+resource (read image disk usage) and names the underlying source (system/df) plus the return fields (total, shared, reclaimable). It is clear but does not differentiate itself from close siblings such as system_df or image_and_volume_bloat.

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?

No guidance on when to choose this over system_df (overall system usage) or image_and_volume_bloat (bloat analysis), and no exclusions or prerequisites. Usage is only implied by the tool name and the [READ] tag.

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