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

Annotations already declare readOnlyHint and openWorldHint, but the description adds substantive context beyond them: zero cost, zero arguments, the fixed sample limitation, and the guarantee that the output shape and code path are identical to get_product_details. That is meaningful behavioral disclosure the structured fields do not carry.

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?

Front-loaded and largely disciplined, with the core value proposition in the first two sentences. There is mild redundancy — the 'When to use'/'Use instead'/'Returns' block restates points already made in the opening paragraphs — but it stays scannable and short.

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?

For a zero-argument preview tool, the description covers what it does, why it exists, what it costs, what it returns (mirroring get_product_details, with an output schema backing that up), and why the page cannot be chosen. Nothing an agent needs in order to call it correctly is missing.

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?

Zero parameters, so the baseline is 4; the description affirmatively confirms 'It takes no arguments,' which removes any ambiguity. There is nothing more to document, but it doesn't need to go beyond that confirmation.

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?

States a specific verb and resource ('run a real extraction against one fixed sample product page') plus the key constraint (no arguments, fixed page). It explicitly contrasts itself with get_product_details, so an agent can distinguish the free preview from the paid sibling without reading either schema.

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?

Gives explicit when-to-use ('Before paying, to see exactly what get_product_details returns'), an explicit when-not-use with reasoning ('pointing a free endpoint at arbitrary URLs would just be the paid tool with no toll'), and names the alternative to use instead. All guidance an agent needs to route correctly is present.

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