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

Annotations already declare it is a non-readonly, non-idempotent, non-destructive write with no open-world access. The description goes beyond them by disclosing the side effects (video creation plus one link per recipient) and the return payload (video, share link, per-recipient links), which matters since there is no output schema. It omits auth requirements or failure/retry behavior for a multi-part join.

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?

A single tight sentence: the action and its prerequisite come first, followed by the return values. No filler, no repetition of the title.

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?

With no output schema, the description compensates by summarizing the return shape, and it covers the cross-tool workflow dependency. It leaves some operational detail unstated (what happens to an expired/incomplete upload, partial failure semantics), but the essential picture for correct invocation is present.

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 71%, so the schema documents most parameters (slug, parts, title, duration, recipients) on its own. The description only adds light framing, notably that recipients produce 'one tracked link each' and that parts come from an in-progress upload. That is marginal added meaning over the schema, fitting the baseline 3.

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 specific verbs and resources: joining upload parts, creating the video, and generating one tracked link per recipient. It explicitly ties itself to the sibling create_upload as the finishing step, so an agent can distinguish it from create_upload, upload_video, and create_link without opening schemas.

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?

Clearly establishes the prerequisite chain ('an upload started with create_upload'), which tells the agent when this tool applies. It does not name an alternative or state a when-not condition (e.g., versus upload_video or create_link), so it falls short of a full routing guideline.

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