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

The annotations already establish write, destructive, and idempotent behavior, and the description adds useful semantics: only sent keys change and empty values clear the main/reference asset fields. That extra context is valuable, though it could further warn about dependency effects or failure conditions when clearing assets.

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?

The description front-loads the write intent and packs substantial field semantics into a compact block with no obvious filler. However, the long parenthetical sentence is dense and slightly harder to parse than it needs to be.

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?

Given the nested updates object, destructive annotation, and lack of output schema, the description covers the essential field meanings, partial-update behavior, and readiness precondition. It does not mention the return value or error behavior, but those gaps are relatively minor for this edit operation.

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 coverage is 0% and the updates object is untyped with additionalProperties, so the description carries the full burden. It succeeds by documenting character_name behavior, the DRAFT/READY enum, and the meaning of character_main_asset_id and character_reference_asset_id, including the effect of empty values.

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 uses a clear verb+resource ("Change fields of a character") and enumerates the editable fields, including status and asset IDs. It distinguishes this from create_character by noting the shared key set and partial-update behavior, so an agent can identify the tool’s scope without opening the 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 gives clear context for editing an existing character and states the READY precondition for downstream image/video tools. It does not explicitly compare against siblings such as set_character_main_asset or explain when not to use this tool, so it falls short of full alternative routing.

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