Get disk statistics

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

Annotations already provide readOnlyHint=true and openWorldHint=true, and the description consistently states "Read-only; never modifies NAS state." It adds helpful context beyond annotations by revealing that the return shape is "whatever the NAS API exposes and is not normalized," which sets expectations about variability. No contradictions.

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 well-organized with the core action first, followed by usage context, read-only note, and sibling differentiation. It is slightly redundant with the annotation ("Read-only; never modifies NAS state") but every sentence otherwise adds value and nothing is extraneous.

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 diagnostics tool with an output schema present, the description covers all necessary aspects: purpose, usage triggers, read-only guarantee, return shape variability, and distinction from the closest sibling. There are no gaps that would prevent correct selection or invocation.

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 has zero parameters and the input schema is empty, so there is nothing for the description to clarify beyond what the schema already reflects. The description appropriately focuses on behavior, not parameters, matching the baseline for a no-parameter tool.

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 action and resource: "Return raw disk statistics reported by the ZSpace NAS." It clearly differentiates from the sibling zspace_pool_info by noting the raw, unnormalized shape versus normalized pool info, so an agent can distinguish them immediately.

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?

Explicit use cases are given: "Use for diagnostics and health monitoring (I/O, capacity, SMART-style counters as exposed by the NAS API)." It also provides a direct exclusion and alternative: "choose pool_info for 'how much free space', this one for 'is a disk unhealthy'." This leaves no ambiguity about when to use the tool.

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