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

Annotations already declare this is a read-only, closed-world lookup, so the safety profile is covered. The description adds real value beyond them by disclosing the scope of the answer — attachment method, wireless charging capability, and store case availability — which tells the agent what it will learn plus a store-specific inventory dimension.

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?

One sentence, front-loaded with the verb and resource, then the three checks in the order the agent would report them. No filler and nothing redundant with the title.

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?

No output schema exists, so the description must convey the return content, and it does so thoroughly for a simple two-parameter read tool. Minor gap: it doesn't indicate what happens for an unrecognized or unsupported phone model, nor whether the case answer includes purchasable identifiers.

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?

Schema coverage is 100%: both parameters carry descriptions and lang has an explicit enum. The description adds no format or syntax guidance for 'phone' (e.g., how to normalize model names) beyond the schema's example, so the standard baseline of 3 applies.

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 names a specific verb ('check') and lays out exactly three facts the tool resolves: direct magnetic attachment vs. need for a case, wireless charging support, and whether a case is sold for the model. This is clearly distinct from siblings like get_product_details or search_products, which deal with catalog data rather than per-phone compatibility.

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 three-question framing makes the triggering situation obvious (a customer asking about their specific phone and the magnetic power bank), but no sibling is named and there is no explicit 'do not use for X' boundary — e.g., it doesn't say to use get_product_details for general specs instead.

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