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

No annotations are provided, so the description carries the full burden. It does disclose the behavioral consequence (this image anchors identity across generated views and shots), but omits whether the change is reversible, what happens to the previously primary reference, and what the required expectedVersion implies about concurrency or failure modes.

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?

A single well-formed sentence with the action front-loaded and the downstream effect immediately following. Nothing is wasted, though it could carry one more sentence of guidance without becoming bloated.

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 four-parameter mutation with no annotations and no output schema, the definition is thin: it explains the semantic effect well but says nothing about version conflicts, failure behavior, or return values. The agent could call it, but not confidently predict what a stale expectedVersion will do.

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 0% across four required parameters, and the description only vaguely gestures at referenceId ('which reference image'). projectId, characterId, and especially expectedVersion — which appears to be an optimistic-concurrency token — are left entirely unexplained in both schema and description.

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 ('choose') and resource ('reference image') and describes the effect: it anchors the character's identity in generated views and shots. That distinguishes it from add_reference/remove_reference in intent, though it never names those siblings explicitly.

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 rather than stated: the mention of 'generated views and shots' tells the agent why a primary reference matters, but there is no explicit guidance on when to call this versus character.add_reference or character.remove_reference, nor any prerequisite such as the reference already existing.

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