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

Adds real value beyond annotations by disclosing canonical-revision creation, retention of earlier versions, retry reconciliation, and absence of generation/credit cost. It reinforces the idempotentHint with concrete semantics rather than just restating it.

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?

Four tight sentences, front-loaded with the core action and followed by versioning, idempotency, and cost. Every sentence carries distinct information with no padding.

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?

An output schema exists so return values need no explanation, and the description covers versioning, idempotency, and cost. It could add permission/ownership prerequisites, but it is largely complete for a 6-param mutation.

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?

With 67% schema coverage, the two undocumented params are covered here: it binds expectedContentHash to the attachment and explains rightsConfirmed as a rights check. This adds meaning beyond the raw schema names.

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 ('Sets') and a precise resource ('an owned uploaded photograph as a shot's original picture'), which clearly distinguishes it from sibling upload/picture tools like studio_media_upload_url and studio_storyboard_stills_*. An agent can identify the operation 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?

The description implies the context ('owned uploaded photograph', 'confirmed rights', 'no credit charge') but never states when to prefer this over alternatives such as studio_storyboard_picture_changes_prepare or the media upload tools. Usage is inferable but not explicit.

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