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

Annotations already declare not-readOnly, openWorld, non-idempotent, non-destructive, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the result is a temporary (expiring) link and there is an async job fallback governed by wait_seconds. It stops short of stating link TTL, size limits, or whether repeated calls re-download.

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 tight sentences, with the primary outcome front-loaded and the async escape hatch second. No filler.

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 must describe returns, which it does: a temporary link or a job id. For a 4-parameter, single-required-URL tool that is close to complete; only link lifetime and storage/expiry details are left implicit.

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 description coverage is 100%, so all four parameters, including quality format strings and the audio_only default, are already documented. The description's mention of wait_seconds largely restates the schema's own wording, adding little new meaning.

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 (download), resource (video or audio track), and the return value (a temporary download link). The follow-up sentence covers the async fallback path, so an agent knows exactly what this produces without opening the 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?

Explains the wait/failover branch clearly: it completes within wait_seconds for most videos, otherwise hand the job id to get_download_status. It does not explicitly direct the agent to get_video_info before choosing a quality, but the schema's quality description does.

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