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

Annotations already declare a non-destructive, non-open-world write; the description adds real context beyond them: the operation is free, the look propagates to other surfaces (/create, channels, Autopilot), and channel binding is persistent ("from now on"). It does not say what happens when a look is already saved or how failures surface, so it falls short of a 5.

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 front-loaded sentences with no filler; the purpose and effect come first, the call condition last. The parenthetical about the card's Save button is slightly tangential but earns its place as a guard against redundant calls.

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 only three fully documented parameters and no output schema, the description covers what an agent needs: what is persisted, where it shows up, and when to call it. The remaining gap is behavior on repeat saves or invalid lookIds, which is minor for this tool's complexity.

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 three parameters (lookId, name, channel) are already documented in the schema. The description restates the channel-by-name behavior and does not add format, precedence, or edge-case meaning beyond what the schema provides, so the baseline of 3 applies.

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 and resource ("Saves a designed look as one of the user's own looks") and immediately clarifies the outcome surface (the look picker here and in ClipFlux). It implicitly separates itself from design_look by naming it as the producer of the lookId, so an agent can tell that design_look creates the design while save_look persists it.

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?

Explicitly bounds invocation: "Call it only when the user wants to keep the look," and explains that the card's Save button already handles saving, which is a concrete when-not-to-call condition. The optional channel-assignment path is also described, leaving little to inference.

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