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

The description adds significant behavioral context beyond the readOnly/idempotent annotations: the 50-credit cost, the 402 error on complimentary plans, id ending in -plt, and the MM/MVM voice mode distinction. This goes well beyond the annotations and helps the agent anticipate real-world 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?

The description is dense and information-rich, with every sentence contributing useful guidance. It is not as crisp as a two-sentence definition, but the extra length is justified by the pricing, plan, and work-flow details. A bit more structure or bullet-like separation would improve scannability.

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 that this tool has no parameters and an output schema exists, the description covers the essential selection and invocation context: when to use it, what it costs, plan limitations, error behavior, and how to proceed after listing. Nothing critical for correct use 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?

The tool has zero input parameters, so there is no parameter surface for the description to clarify; an empty schema already communicates this. The description's additional notes about credits, plans, and ids are not parameter-level but are still useful context. Baseline 4 is appropriate for a no-parameter tool.

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 identifies the tool as listing platinum films: 'the platinum shelf: studio-grade films'. It differentiates from list_films by naming the normal-film sibling and explaining the credit cost difference. The verb 'list' and resource 'platinum films' are explicit and unambiguous.

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 gives explicit when-to-use guidance: 'Offer one only when the human is making a big launch they genuinely want to go far', and explicitly routes everyday/normal-budget cases to 'list_films'. It also provides operational guidance like saying the price before rendering and using describe_film for the body.

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