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

Adds real behavior beyond the annotations: no credit cost ('Free'), an ownership/authorization scope ('Only the user's own'), the 48-hour retention constraint on the underlying footage, and that status updates arrive without manual polling ('The player card checks on its own'). The last phrase is terse and slightly opaque about whether the caller must poll, which keeps this short of a 5.

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 action and kept to a handful of short sentences with no filler. The telegraphic, fragment-heavy style ('Free.' / 'Only the user's own.') reads as clipped rather than fully structured, costing a little clarity.

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 one-parameter tool with an output schema, the description covers the decisive facts: what is rebuilt, cost, ownership, the retention deadline, and the fallback tool. Return-value behavior is correctly left to the output schema, so nothing essential is missing.

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 parameter with 100% schema description coverage ('The failed video id.'), so the schema already carries the semantics. The description adds nothing about the id's origin or format beyond what the schema states, so the 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 ('Rebuild a failed finished video') and narrows it further by naming the inputs reused ('same clip, hook and footage'), which cleanly separates it from make_video and from the sibling retry_clip/retry_image tools.

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 both the when ('a failed finished video', footage still stored) and the when-not ('otherwise make_video again with fresh footage'), naming the alternative tool explicitly. The 48-hour footage window is stated as the concrete condition that selects between the two.

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