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

Annotations already declare the safety profile (not read-only, not idempotent, not destructive), and the description adds meaningful async context: it returns workflowRunId/projectId/projectUrl and that progress and downloadUrl come via get_workflow_run after auto-export. This tells the agent the call is a long-running job requiring polling, which annotations alone would not convey.

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 tight sentences, front-loaded with purpose, then prerequisite, then the avatar parameter path, then returns and the next step. Every sentence carries actionable content 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 complex 9-parameter async creation tool with nested objects, the description covers the source prerequisite, the optional avatar branch, and the polling follow-up, and an output schema exists so return values need not be enumerated. It is close to complete, though the theme/autoExport decision points are left to the 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%, so the schema already documents all nine parameters, including the upload relationship for fileId and the avatar conditions. The description reinforces the fileId prerequisite and avatar path but adds little beyond what the schema descriptions already state, so baseline 3 applies.

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 ('Build an editable narrated video') and scopes the input source ('from an uploaded PDF or slideshow file'), which distinguishes it from sibling video tools that take scripts, storyboards, or voiceovers. It stops short of naming those siblings explicitly, so differentiation is implied rather than stated.

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 a concrete prerequisite chain ('Upload the file first with upload_file, then pass its fileId') and conditional guidance for the avatar path ('For avatar narration, pass actorEntityId and optionally set avatarQuality'). It does not say when to prefer this over voiceover_to_video or script_to_video, so no explicit alternatives or exclusions.

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