Known Folders

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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds useful behavioral context beyond the annotations: 'No permission required', iCloud Drive included conditionally, and the specific resolved-path/existence/allowed-path output. This enriches the agent's understanding of runtime 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?

The description is a single dense sentence that front-loads the action and resource, then packs in the folder list and output fields. Every clause carries useful information, with no fluff or redundant restatement.

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?

Given no output schema, the description fully explains the return values (resolved path, existence, allowed-path status) and notes the environmental dependency on MACCTL_ALLOWED_PATHS. The input side is trivial (no parameters), so the description is complete for the tool's actual complexity.

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, making schema coverage 100% trivially. The baseline for 0 parameters is 4, and the description does not need to add parameter-level detail since there are none to document.

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 uses the specific verb 'List' with the resource 'well-known macOS folders', enumerating the exact folders and the output attributes (resolved path, existence, allowed-path membership). This clearly distinguishes it from sibling tools like file_list or file_search.

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?

The description implies usage through context—listing standard macOS folders without requiring permissions—but does not explicitly state when to prefer this tool over alternatives like file_list or file_search. No exclusions or alternative comparisons are provided.

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