feature_shell

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

With no annotations provided, the description carries the full burden and does so well: it discloses atomicity ('nothing changed'), rollback on failure ('rolled back'), the exact error codes (INVALID_PARAMS, FUSION_API_ERROR), and which result field reports the mutated bodies. This is materially more than the schema supplies.

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 purpose, then usage rules, then errors, then return shape, then a concrete example. Every block earns its place; nothing is padding.

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?

Although there is no output schema, the description enumerates the returned keys ({feature, health, created_bodies, modified_bodies, removed_bodies}) and documents failure modes and units. An agent has everything needed to invoke it correctly and interpret the result.

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 100%, so baseline is 3. The description adds real meaning on top: the faces-vs-bodies tradeoff (open box top face vs closed hollow body), the ability to combine inside and outside thicknesses, and that thicknesses may be Fusion expressions in addition to plain numbers in `units`.

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 opening sentence gives a specific verb and resource: 'Hollow a body into a shell with walls of the given thickness.' That is far more precise than a restatement of the name. It does not, however, differentiate from adjacent siblings such as body_thicken or feature_offset_faces, which an agent might reasonably confuse with shelling.

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?

The description gives clear operating rules — pass faces (open shell) OR bodies (closed hollow body), plus inside_thickness and/or outside_thickness — which tells an agent how to compose a valid call. It stops short of naming alternatives or stating when to choose shelling over body_thicken/offset faces, so there is no explicit exclusion guidance.

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