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

Beyond the annotations (destructive, non-idempotent, non-read-only), the description discloses that minutes are charged under the same rule as approval, that an already-charged lesson 'holds nothing new', that account limits and the key's cap still apply, and that the live video keeps serving until the new one lands. That is substantive side-effect and cost detail not present in the structured fields.

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 message is front-loaded with the action and the cost warning, and most sentences earn their place. The parenthetical opening line ('the minutes rule is the approval's own') is slightly cryptic and reads as filler before the clearer explanation that follows.

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 single-parameter destructive mutation with no output schema, the description covers preconditions, cost model, and live-video continuity well. It stops short of saying how to verify the new render or what the call returns, which would complete the picture.

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?

There is a single required 'id' parameter with 100% schema description coverage, so the schema already carries the parameter meaning. The description does not add format or validation detail for the id beyond the surrounding status precondition, which is the expected baseline when schema coverage is high.

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 ('Render a finished lesson again', 'Draws the lesson's current approved storyboard again: same scenes, new video'), and contrasts this against editing ('re-rendering after an edit is this call'), so an agent can distinguish it from approve_lesson and edit_lesson.

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?

It gives an explicit precondition ('Only a lesson whose status is done can be rendered again'), tells the agent this is the correct follow-up to an accepted edit, and warns to 'confirm with the owner first' because minutes are spent. Both when-to-use and when-to-be-cautious are covered.

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