Workspace Roots

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

Annotations already establish readOnlyHint=true, and the description adds meaningful context beyond that: it explains where the allowed directories come from (CLI arguments, FS_ALLOWED_DIRS, --allow-cwd). This gives the agent useful operational knowledge about the tool's behavior and configuration without contradicting the annotations.

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?

Three tight sentences, each earning its place: the primary action, the critical usage instruction, and the configuration sources. The most important information 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 parameterless, read-only listing tool, this is complete. It tells the agent when to call it, what it returns conceptually (accessible paths), and how those roots are configured. No output schema exists, but the description sufficiently implies a list of path strings.

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 takes zero parameters and the schema is empty, so there is nothing for the description to document. The baseline for 0 params is 4, and the description appropriately avoids inventing parameter details, keeping the tool's parameterless nature clear.

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?

States a specific verb ('List') and a specific resource ('allowed workspace root directories'), and immediately clarifies how it differs from the file-operation siblings: every other tool is scoped to these roots. An agent can distinguish list_roots from the generic 'list' sibling without opening schemas.

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 instructs the agent to 'Call this first' and explains why — the results determine which paths are accessible to all other tools. This is clear, actionable usage guidance that leaves no ambiguity about when this tool should be invoked.

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