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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely new behavioral context: no money is charged here, payment only occurs after opening the checkout and confirming, and post-payment sign-in is required. It stops short of describing link expiry or reuse behavior.

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-loads the purpose and then walks through the account-specific flows in short, purpose-driven sentences. The final sentence about signing in after payment is slightly tangential but still earns its place by closing the loop.

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 no-output-schema, single-parameter link generator, the description covers purpose, timing, and the surrounding account flow well. The notable omission is claim_token semantics, which leaves the only input underspecified.

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 single parameter claim_token is described only in the schema's top-level note ('required for a signed-out sample checkout'); the tool description never mentions it at all and offers no guidance on when it is needed versus omitted. With 0% property-level schema coverage and one undocumented parameter, the description fails to compensate.

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 concrete verb+resource ('Returns a checkout link') and scopes it to two cases (monthly plan or one-time top-up). It differentiates itself from workflow siblings by naming sign_in and create_video, though it never explicitly contrasts with get_sample_status or get_video_sample.

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?

Explicitly routes the agent: existing accounts should call sign_in then create_video to consume credits first; new accounts should call this once the sample is ready. It states both the when and the when-not, with named alternatives.

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