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

Annotations already declare non-read-only, open-world, idempotent and destructive, so the safety bar is partly covered. The description usefully adds that no media is generated, that a canonical element ID is returned, and that reference images must be existing Library assets. It does not address the destructiveHint=true annotation at all (what could be overwritten or lost), which is a meaningful gap for a mutation tool.

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?

Four short, front-loaded sentences with no filler: purpose first, then 3D context, then return value, then constraints. Tight and scannable, though it could have spent a clause routing to the 3D sibling instead of the somewhat cryptic workshop note.

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?

With an output schema present, return-value detail is optional, and the description still mentions the canonical ID. But for a six-parameter mutation tool with nested objects and a very close sibling (native.create_three_d_element), the definition leaves the 3D path and the read_skills proof requirement unexplained, so an agent could still pick the wrong tool or under-supply required inputs.

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 50%, so the baseline is 3. The description does add meaning for the images parameter (must reference existing Library assets), but says nothing about the required work_id, request_key, read_skills proof requirement, or the enum-like kind values beyond restating them. It does not compensate for the half of the parameters left undocumented.

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 concrete verb (Create) plus the resource and enumerates the supported kinds (character, set, prop, three_d), so the purpose is unambiguous. However, it overlaps with the sibling native.create_three_d_element without telling the agent which one to pick for 3D elements, so it fails the sibling-differentiation bar for a 5.

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 implicit routing cues ('Does not generate media') and a prerequisite for reference images, but never names the alternative tools (e.g. native.generate_element_take for media, native.create_three_d_element for three_d) or states when this tool should be chosen over them. Usage is implied rather than explicit.

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