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

The description provides rich operational details, such as specifying that sending an empty value clears a field, defining the semantic difference between main-stage and reference assets, and limiting the change scope ('Only the keys sent change'). This adds significant context beyond the annotations and schema.

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 is highly dense and packed with critical information, but its structure is slightly long due to the technical nature of the data it conveys. Every piece of information, however, is essential and well-placed.

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 complexity (multiple asset IDs, state dependencies, and external key compatibility), the description is perfectly complete. An agent requiring an update to a character would have every constraint and detail needed to call this tool correctly.

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?

With 0% schema description coverage, the description carries the entire semantic burden. It explains that the `updates` object accepts all keys from `create_character` plus three new ones, thoroughly compensating for the missing structured documentation.

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 clearly states the action ('Change fields of a character') and defines the scope by referencing existing keys from create_character, while specifically enumerating three new fields and their meanings. This makes it impossible to confuse with other character-related tools.

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 establishes a critical prerequisite rule: the character must be READY before it can be used in image or video creation functions. This directly guides the agent on sequencing and usage constraints against related tools.

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