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

Annotations only declare that this is a non-read-only, non-idempotent, non-destructive write. The description adds real behavioral context: the permission requirement, the optimistic-concurrency gate on expectedRevision, the reversal semantics of passing null, and that no image is created. It omits whether the change is reversible once applied, which keeps it below 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?

Three compact, front-loaded clauses with no filler; the core action, the reversal option, the prerequisites, and the return shape each appear once and earn their place.

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 mutating tool with a full output schema, the description covers the action, the special null case, the concurrency and permission prerequisites, and even notes that no image is generated. Nothing an agent needs in order to invoke it correctly 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?

Schema description coverage is 100%, so all three parameters are already documented in the schema (including the null-means-automatic semantics for referenceId and the stale-revision refusal). The description restates the null case and clarifies that expectedRevision comes from the current profile, but adds little beyond structured data. Baseline 3 is appropriate.

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 ('sets an existing passed DNA photograph as the artist cover') and distinguishes itself from neighboring cover mechanisms by specifying the DNA-photo source. The phrase 'creates no image' further separates it from generation tools like studio_artist_dna_write or studio_artist_photo.

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?

Gives a clear conditional for the null case ('referenceId:null restores automatic cover selection') and states activation prerequisites (artist permission, expectedRevision from the current profile). It does not explicitly contrast against the sibling cover tool studio_artist_ready_made_choose, leaving that inference to the agent, so it stops short of a 5.

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