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

The description adds substantial behavior beyond annotations: it reveals the async job pattern, the billing condition ('Charges credits only on success'), and the API-key requirement with setup URL. Annotations only state read/write/idempotent/destructive hints; the description enriches the contract with operational and auth details, with no contradiction.

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?

Four sentences, each earning its place: purpose, async workflor, cost guidance, auth requirement. The most important fact leads, and the description is compact with no filler.

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 mutation tool with an output schema and five documented parameters, the description covers everything an agent needs to call it correctly: what happens on invoke, how to track the job, cost implications, and mandatory auth setup. No significant gap.

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 description coverage is 100%, so the baseline is 3. The description does not add any parameter-specific semantics beyond what the schema already provides, but it doesn't need to; the schema documents all five parameters adequately.

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 opens with a specific verb-resource pair ('Start generating an AI video') and immediately clarifies the asynchronous contract ('Returns a job id immediately — poll get_generation'). It distinguishes itself from the sibling get_generation by naming the polling relationship, so an agent can tell initiation from status-checking without opening other schemas.

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 to alternatives: 'poll get_generation until status is completed' names the follow-up tool, and 'Call estimate_credit_cost first if the cost matters' states the condition for using the cost estimation sibling. This gives clear when-to-use and when-to-use-other guidance.

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