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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the agent knows this is a safe, open-world read operation. The description adds that the result includes item counts, dates, and links, which is useful context. It doesn't disclose pagination, freshness, or whether the list is exhaustive, but the openWorldHint covers some of that.

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, information-dense sentence that front-loads the main purpose and then lists the output fields. It is concise and every part adds value, though the long parenthetical list of directory examples is somewhat bulky.

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 zero-parameter, read-only listing tool with no output schema, the description adequately tells the agent what it will get: directory names, item counts, dates, and links. It doesn't specify the output format, but the absence of parameters and the simple listing nature make this a minor gap.

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, so the description doesn't need to explain parameter meaning. The baseline for 0 params is 4, and the description appropriately focuses on what the output contains rather than input semantics.

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 the tool lists the site's directories, their item counts, dates, and links, with a specific verb ('list') and resource ('directories'). It doesn't explicitly differentiate from siblings, but the resource and detail level are distinct enough among the sibling names.

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: call it to see which directories exist and their sizes/dates/links. It doesn't explicitly state when to use it versus alternatives, but given zero parameters and a listing purpose, the context is reasonably clear. No exclusions or alternative routing are provided.

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