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 '[write]' tag adds nothing and the safety profile is covered. The description does add real semantic context (what the main asset is used for and how it differs from the reference asset), but it never says what the destructive replacement does to a previously set main asset.

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?

Front-loaded with the action and scoped with a tight parenthetical, then one short contrasting sentence. The '[write]' prefix duplicates the annotation, but otherwise there is little waste.

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 two-parameter write tool with no output schema and full annotation coverage, the description supplies the essential conceptual model and cross-tool references. The remaining gap is the effect on any existing main asset, which matters given destructiveHint=true.

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%, so the description has to carry the load; it does a good job on `asset_id` (MAIN-stage asset retrieved via get_character) but leaves `character_uuid` entirely unexplained. Partial compensation justifies a mid score rather than the 4 baseline for undocumented params.

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 ('Choose the main picture') and the exact resource semantics: a MAIN-stage asset that represents the character in images and videos. It also explicitly separates this from the sibling concept `character_reference_asset_id` set via edit_character, so an agent can tell the two apart without opening either 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?

It states where the input comes from ('`asset_id` from get_character') and routes the alternative concept to edit_character. That gives clear context for use, but it never states an explicit precondition (e.g. the asset must already be MAIN-stage) or a 'do not use this for X' exclusion.

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