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

Annotations carry only a title, so the description bears the disclosure burden and does well: it names the default mode, states that render=true queues (not completes) the render, and that captions are computed server-side with 'no frame math needed.' It stops short of saying what the call returns or what permissions are required, which is the only notable gap.

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-loaded with the verb and resource, then mode/default, then the sibling escapes. It is dense with em-dash-heavy clauses but nearly every clause carries distinct information (modes, defaults, alternatives, captions behavior), with little padding.

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 an 8-parameter tool with nested track/caption objects and no output schema, the description covers modes, defaults, input dialects (simplified tracks[] vs raw GUI schema), and how to get render status, which is enough to call it correctly. It could still say what a successful call returns (project id / job id), but the sibling hand-off mitigates that.

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 already 88%, so the schema documents name, assets, render, schema, tracks, captions, resolution and aspect_ratio in detail. The description mostly restates those fields; its only added semantic is that 30fps frames are canonical and 'seconds fields are converted exactly.' Baseline 3 is appropriate given the schema does the heavy lifting.

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 states a specific verb and resource ('Build a PRECISE multi-track video timeline ... save it as an editable project or queue the render') and contrasts itself against siblings by name (var2_join_videos, var2_check_join_status). An agent can distinguish it from var2_join_videos and var2_create_video without opening any schema.

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?

Explicit routing: 'For simple back-to-back concatenation use var2_join_videos instead' and 'status of a queued render → var2_check_join_status.' It also gives the mode condition (render=false = save project, render=true = queue render) up front, so the when-to-use decision is fully specified.

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