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

Annotations already declare a non-read-only, non-idempotent, non-destructive, closed-world mutation, so the safety profile is covered. The description adds genuinely useful context beyond that: a concrete cost of '30 credits' and the fact that this is a prerequisite stage in the animation pipeline. It could go further by noting that re-running on an already-rigged model may replace or stack a rig (relevant since idempotentHint=false means repeat calls cost credits again).

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?

Two sentences, zero filler: capability and scope first, then the ordering constraint, then the cost. Each sentence carries distinct decision-relevant information and the most important framing is front-loaded.

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 one-parameter mutation with full schema coverage, annotations, and no output schema, the description covers purpose, pipeline position, and cost. The main remaining gap is the return/effect model — whether the input asset is modified in place and how the agent learns the rig succeeded — which matters given no output schema exists.

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?

There is a single parameter and the schema description coverage is 100%, so the 'id' field is already fully documented as a 3D model asset ID. The description adds no meaning about the parameter — no note on where the ID comes from (e.g., list_assets or generate_3d_model) or what to expect if the asset is not a 3D model. Baseline 3 applies when the schema does the heavy lifting.

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 gives a specific verb and resource ('Add a skeleton to a 3D model') and immediately bounds the scope with three concrete rig categories (humanoid, four-legged animal, prop moving parts such as a chest lid or door). This clearly separates it from siblings like animate_3d_model or generate_3d_model, so an agent can pick it 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 states an explicit pipeline prerequisite: 'Run before animate_3d_model,' naming the sibling and the ordering constraint. It does not state when not to use it (e.g., models that already have a rig, or rigging a sprite), so it stops short of full when/when-not/alternatives coverage.

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