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

Beyond the readOnlyHint and destructiveHint annotations, the description discloses the important conditional behavior around size confirmation and the exact URL variants to emit. It clearly communicates that the tool only constructs links and has no destructive or state-changing side effects.

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 compact and front-loaded with the core action and URL format, followed by a clearly labeled mandatory instruction. There is no filler or redundant restatement of schema details.

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 presence of an output schema, full parameter schema coverage, and annotations, the description covers the key decision rule and URL construction behavior completely. The agent has enough information to invoke the tool correctly and know what to return.

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 already covers all parameters with 100% description coverage, so the baseline is 3. The description adds value by mapping handle and size_index to URL path positions and by tying size_index to the user's explicitly confirmed size selection. Coupon and quantity semantics are left to the schema, which is acceptable.

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 immediately states the specific action: generating the direct 1-click checkout purchase URL for a product and size index, and includes the exact URL template. This clearly distinguishes the tool from unrelated siblings such as product search or stock-checking tools.

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 mandatory instruction explicitly tells the agent when to include /{size_index} (only after the user confirms a size) and when to return the clean base link instead (if the user is still browsing or sizes are unclear). This provides clear when-to and when-not-to guidance.

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