list-accounts

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

No annotations exist, so the description fully carries the burden. It discloses an important error behavior: if AppleScript transport fails, it returns an ERROR rather than an empty list, and an empty list always means truly no accounts. This goes beyond basic listing semantics and adds valuable transparency.

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?

Four concise sentences with clear structure: Use when, Returns, error caveat, Do not use when. Every sentence contributes useful information with no fluff.

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 simple zero-parameter tool, the description fully covers purpose, usage, error behavior, and exclusions. The output schema likely handles return structure, and the description adds the critical distinction between an error and an empty list, making it complete.

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 baseline is 4 per the rubric. The description adds context about the output (account names and count) and emphasizes passing an 'exact account name' to other tools, but there is no parameter detail to add. It appropriately does not invent unnecessary info.

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?

Clearly states it lists configured Mail accounts (like iCloud, Gmail) and the purpose is to get an exact account name for other tools. It explicitly distinguishes from list-mailboxes (folders) and list-messages/search-messages (messages).

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?

Provides explicit 'Use when' and 'Do not use when' sections, including named alternatives (list-mailboxes, list-messages, search-messages). This gives clear context for when to invoke this tool vs siblings.

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