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

Discloses read-only nature, no side effects, and lists supported behaviors (recursive depth, hidden files, symlink following, etc.). This adds significant context beyond annotations that only indicate readOnlyHint.

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 sentences: the first packs essential info, the second lists exclusions and alternatives. Every word is necessary; no fluff or repetition.

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?

Accounts for all 7 parameters, describes output format (structured JSON with metadata fields), mentions streaming for large directories, and references siblings. No output schema exists, so the description compensates well.

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?

With 100% schema coverage, baseline is 3. The description summarizes the main parameter categories (recursive depth, hidden files, etc.), adding semantic grouping and context that aids understanding beyond the schema's individual parameter explanations.

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 clearly states 'List directory contents as structured JSON with per-entry metadata', providing a specific verb and resource. It distinguishes itself from siblings by naming alternatives and their purposes.

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?

Explicitly tells when to use ('programmatic directory inspection') and when not to use (e.g., 'Not for column-aligned output — use dir'). Provides specific alternative tool names, giving complete guidance.

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