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

Goes beyond the annotations meaningfully: it discloses that bytes go directly to a third party (Brix36) rather than through the tool, that the fallback uploadUrl is one-time, and that re-calling returns the same link or existing attachment. It also states 'No charge,' which no annotation covers. Idempotency is restated from the annotation but confirmed semantically.

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?

Three tight sentences with no filler, each adding distinct information (return artifact, byte destination, idempotency/cost). Front-loaded on the return value rather than the action, but still efficient and readable.

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 tool with an output schema and rich annotations, the description covers the remaining gaps an agent needs: what is returned, where data flows, repeat-call behavior, and cost. Nothing material 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?

Only one parameter with 100% schema coverage, and the schema already ties projectId to studio_video_start. The description's 'existing project' phrasing adds only a weak forced-existence constraint beyond what the schema provides.

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+resource: it returns a song upload widget and a one-time fallback uploadUrl for an existing project. The 'song' scope clearly separates it from generic media-upload siblings, but no sibling is actually named to route the agent. Clear but without explicit differentiation.

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?

Usage is implied by 'for an existing project' and the chat-upload framing, but there is no explicit when-to-use, when-not, or alternative routing (e.g. vs studio_media_upload_widget or the other song tools). The agent must infer the trigger condition.

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