set_face_sets

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

With no annotations, the description carries the full burden; it does disclose the return shape (count of distinct face sets) and the ASSIGN-only constraints. However, it never says whether non-ASSIGN modes overwrite or destroy existing face sets, whether CLEAR removes all sets or only the target, or whether the mesh must already be in sculpt mode — key behavioral facts for a mutating operation.

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 a short sculpt-mode rationale, then structured Args/Returns. Every block is useful, though the sculpt-mode paragraph is context an agent could live without and slightly delays the parameter detail.

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?

An output schema exists, so the return-value sketch is supplementary rather than necessary, and all four parameters are documented. For a four-parameter mutation with zero annotation coverage, it is nearly complete — only the overwrite/destructive semantics of the non-ASSIGN modes are missing.

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%, so the description must compensate and largely does: it defines all four mode enum values, scopes face_indices and face_set to ASSIGN, and adds the '1 or more' lower bound on face_set. Minor gaps remain — the face_set default of 1 and face_indices defaulting to null are not mentioned.

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 and resource — split a mesh into face sets — and immediately explains what a face set is (colored regions for sculpting one part at a time), which no sibling tool does. An agent can identify the operation and its scope without further inference.

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 mode breakdown effectively gives when-to-use guidance for each variant (LOOSE_PARTS for separate pieces, MATERIALS per material slot, ASSIGN for explicit faces, CLEAR to remove), and the sculpt-mode paragraph situates it in a workflow. It stops short of naming adjacent tools (set_sculpt_mask, enter_sculpt_mode) as alternatives or stating when not to use it.

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