Start a render

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

With no annotations, the description fully covers behavioral traits: asynchronous behavior, credit reservation, return fields, polling mechanism, error handling (HTTP 402), authentication via environment variable, watermarking based on key prefix, and independence of API base URL. No contradictions.

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 a single paragraph that efficiently conveys multiple pieces of information. It is not overly verbose, but could benefit from slight structural organization (e.g., bullet points) for easier scanning.

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 tool's complexity (asynchronous, nested parameters, authentication, credit system), the description is remarkably complete. It covers return values, error conditions, asset constraints, and polling instructions, leaving no major gaps despite lacking an output schema.

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 coverage is 100% with descriptions for each parameter. The description adds valuable context beyond the schema, such as the URL requirement for asset references and the authentication environment variable details, enhancing understanding for the agent.

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 states the tool's function: 'Submit a Movie definition... and start an asynchronous render.' It specifies the verb, resource, and outcome, and distinguishes from siblings like get_status (polling) and validate (validation).

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 provides explicit context for use: when to start a render, requirements (credits, URLs, authentication via environment variables), and how to proceed (poll with get_status). It does not explicitly say 'when not to use' but implies alternatives via sibling tool mentions.

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