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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false, so the safety profile is covered; the description adds the genuinely useful behavioral fact that this is a human-in-the-loop handoff — it returns a page the person must act on, not a completed upload. It also closes the loop by stating the video later shows up in list_videos and its clips in list_clips, which is exactly the follow-up an agent needs. Missing are link expiry and whether an auth session is required to use the returned page.

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?

Two sentences, no filler: the first states what is returned and the condition that triggers it, the second states the downstream consequence. The most important information is front-loaded.

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 zero-parameter, non-mutating tool with no output schema, the description covers the essentials an agent needs: what it gets back (a page), who acts on it (the person), and how to detect the result afterwards. The only omissions are minor operational details like link lifetime.

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?

The tool takes zero parameters, so there is no parameter semantics to add and the baseline of 4 applies. Nothing in the description conflicts with the empty schema.

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 gives a specific verb and resource ('Returns the SnapDub page where the person can upload a video file from their device') and adds a scoping condition ('for a source that is not on a public link'). That makes the purpose unambiguous, though it never explicitly names create_video as the contrasting tool for sources that already have a public URL, so sibling differentiation is only implicit.

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?

The clause 'for a source that is not on a public link' is a real when-to-use condition that steers an agent to this tool only when no fetchable URL exists. It stops short of an explicit alternative ('if you have a public URL, use create_video instead'), so the exclusion has to be inferred rather than read.

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