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

With no annotations, the description carries the full burden. It discloses the diagnostic (non-mutating) nature, the specific areas checked, and the return format (formatted text plus structured checks). It does not explicitly state 'read-only' or mention potential side effects, but the diagnostic framing strongly implies a safe analysis operation, which is sufficient for a zero-parameter tool.

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 three sentences, front-loaded with 'Use when', and includes a return-value note and a clear 'Do not use when' with alternatives. Every sentence earns its place—no fluff or redundancy.

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 the tool's low complexity (zero parameters) and the presence of an output schema, the description adequately covers the purpose, target issues, return type, and exclusions. It provides enough context for an agent to select and invoke it confidently without further detail.

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 0 parameters, so the schema coverage is trivially 100%. Per the calibration rule, a 0-parameter tool receives a baseline of 4, and there are no additional parameter semantics needed since no inputs exist.

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 diagnoses Mail.app automation permissions, account state, and IMAP/SMTP backends, which is a specific verb+resource+scope. It also distinguishes itself from siblings by naming alternatives like health-check and get-mail-stats, making its purpose unambiguous.

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 provides both 'Use when' conditions (troubleshooting setup problems) and 'Do not use when' exclusions (quick up/down status, message counts), with named alternative tools (health-check, get-mail-stats). This gives clear decision guidance for when to invoke this tool.

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