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

Annotations already declare readOnlyHint=false, destructiveHint=true, and idempotentHint=true, so the safety profile is covered. The description adds nothing beyond that: it does not explain what gets destroyed/overwritten on update, that likeness and reference-rights consent must be confirmed before a human character is applied, or how idempotencyKey governs replay. It essentially restates the annotation-covered mutation behavior.

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 front-loaded sentence with no filler or repetition. It is well-formed, though its brevity is a symptom of under-specification rather than disciplined economy.

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 14-parameter, destructive, consent-gated mutation tool, this description is far too thin. An output schema exists so return values need not be explained, but the create-vs-update branching, consent prerequisites, and idempotency behavior are all 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 2 of 14 parameters carry schema descriptions (~21% coverage), so the description must compensate and largely fails to. 'Reference-based' loosely gestures at referenceAssetIds/primaryReferenceAssetId, but type/species/storyFacts/defaultVoiceId/characterId/canonicalDescription are left with no semantic explanation at the description level.

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?

The description names a specific verb pair ('create or update') and a specific resource ('reference-based character'), and adds the domain ('repeatable faceless story generation'). An agent can distinguish it from the read-only siblings characters_get and characters_list, though it never states that distinction 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?

There is no when-to-use guidance: nothing says when to create vs update (e.g., presence of characterId), when the consent flags are required, or how this relates to characters_get/characters_list or generation_faceless_create. The phrase 'for repeatable faceless story generation' implies context but is not actionable routing guidance.

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