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

Beyond the readOnlyHint annotation, the description adds behavioral details: checks Luhn check digit, recognizes IMEISV, returns TAC, and does not verify device authenticity. No contradictions 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 two focused sentences, front-loaded with an imperative directive, and contains no redundant information. Every sentence adds unique value.

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 (single parameter, no output schema), the description covers the core purpose and limitations. However, it could briefly mention the likely return format (e.g., boolean or object with validity and TAC) to improve completeness slightly.

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?

While schema coverage is 100% and the parameter description already specifies format, the tool description adds value by explaining the validation logic applied to the input (Luhn, IMEISV, TAC extraction), enhancing the agent's understanding of how the parameter is processed.

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 verifies a phone/device IMEI, specifies the resource (IMEI), and distinguishes it from sibling validators by focusing on Luhn check digit and IMEISV recognition. It uses imperative language 'USE THIS' to direct the agent.

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 explicitly says to use this for IMEI verification before relying on it, and clarifies what it does not check (real, active, blocklisted). This directly guides when to use and when not to use, despite not naming alternative tools.

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