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

Annotations already indicate readOnly, openWorld, idempotent, and non-destructive behavior. The description adds further context: it only decodes pre-2021 serials, cannot verify condition or Activation Lock, and is advisory only. No contradiction with 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?

The description is extremely concise (two sentences) yet packed with essential information. The first sentence front-loads the main action and outputs; the second covers limitations. Every word earns its place.

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 simplicity (one parameter, no output schema, comprehensive annotations), the description is complete. It covers what it returns, format expectations, and what it cannot do, leaving no major gaps for an agent to misinterpret.

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 input schema's parameter description already explains the serial format. However, the tool description elaborates on the character length differences (10 for 2021+, 11-12 for older), adding useful context beyond the schema. Schema coverage is 100%, so the description adds incremental value.

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 checks a Mac serial number for an existing Macfax report and decodes model/year for pre-2021 serials. It also specifies what it does not do (verify condition, Activation Lock, possession), making the purpose very specific and 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?

The description mentions what the tool does and its limitations but provides no explicit guidance on when to use this tool over its siblings (e.g., get_mac_report, check_mac_listing). While it implies use for report existence and serial decoding, it lacks direct comparison or when-not instructions.

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