Disk usage

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

Annotations already cover read-only, idempotent, non-destructive, so the bar is lower, yet the description still adds real value: the numbers reflect 'what an unprivileged user may use' (i.e. results are permission-relative, not raw df output) and the default filter omits pseudo file systems and read-only snap images. It does not state units, ordering, or whether one entry per mount is returned.

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 tight sentences: what you get first, the default filter second. No filler, no repetition of the title or annotations.

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?

An output schema exists and annotations carry the safety profile, so the description only needs to scope the data — which it does via the pseudo/snap exclusion and the unprivileged-user framing. Remaining gaps (units, sort order, per-mount granularity) are minor for a single-flag read tool.

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 100%, so the single boolean is already documented as 'also list proc, sysfs, cgroup, squashfs and the like'. The description adds one detail the schema omits — read-only snap images are also gated by this flag — which is useful but marginal, so the baseline of 3 applies.

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?

Names the resource precisely (mounted file systems) and the exact fields returned (size, use, free space, inode use), with a concrete df analogy that pins down semantics. It is trivially distinguishable from the process/port/log siblings, though it never uses an explicit verb like 'list'.

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 by the subject matter — an agent can infer this is the tool for disk capacity questions, but there is no 'use this when' clause and no sibling is named as an alternative. The only routing guidance is the negative default (pseudo file systems excluded unless include_pseudo is true).

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