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

Annotations already declare readOnlyHint=true and destructiveHint=false, but the description adds substantial behavioral context: BLOCKING latency with a 120s timeout, no recursive tree in one shot, Windows-only operation, devices permission requirement, and a safety note that write paths are on a permanent deny-list. This goes far beyond what the annotations convey.

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 long but dense and well-organized: purpose, required parameters, drill-down pattern, safety, latency, permissions, platform constraints, and an example. Every section earns its place and the core purpose is front-loaded in the first 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 tool with no output schema, the description supplies the essential return semantics ('immediate-children size breakdown'), a recursion strategy, latency expectations, and platform constraints. It is complete enough for correct invocation, though the exact response fields and units are left implicit rather than stated.

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 coverage is 100%, so the schema already documents device_id and path. The description adds concrete value by clarifying JSON escaping with an explicit counter-example ('pass "D:\\" not "D:\"') and providing a full example call, which reduces the risk of malformed paths.

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 names a specific verb and resource: 'disk usage report' that 'returns the immediate-children size breakdown for the given path'. It also anchors the purpose with a concrete question ('D: drive is at 95%, what's eating it?') and clearly distinguishes it from generic agent tools by tying it to GETFOLDERUSAGEPATH.

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?

It gives an explicit drill-down usage pattern: start at the drive root, identify the largest child, and recurse. It also states when not to use it — Linux/macOS hosts have no agent-side equivalent — and emphasizes the deliberate non-recursive latency cap, so an agent knows not to expect a one-shot full tree.

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