fillet

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

No annotations are provided, so the description carries the full behavioral burden, and it discloses almost nothing: no statement of what happens if an edge index is invalid or the radius exceeds the body geometry, no note on whether the operation is transactional/undoable, and no indication of which solid is modified. Only the units (mm) are surfaced.

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 core action and units are front-loaded in the first sentence, and the argument list is short and purposeful. The arg lines partially restate the schema, but they add the mm unit and the index-format example, so little is wasted.

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 return values need not be explained. But for a geometry-mutating tool with zero annotations, the definition says nothing about failure modes, target-body selection, or whether the change is reversible — information an agent needs before invoking a destructive CAD operation.

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 only 33%, but the description compensates well: it documents radius units (mm) and specifies the edge_indices format as a comma-separated list with the example "1,2,3", plus a pointer to status() for valid values. The remaining instance parameter is already documented in the schema, so the gaps are effectively closed.

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 first sentence gives a clear verb and resource ('Add fillet (rounded edge) to edges of the solid body') and even glosses the term 'fillet', so an agent unfamiliar with CAD terminology understands it. It does not distinguish itself from the sibling chamfer tool, which is the nearest alternative operation, so it stops short of 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?

There is one concrete usage hint: 'Use status() to see edge count' for discovering valid edge_indices. However, it never says when to choose fillet over chamfer, which body it applies to when multiple exist, or any precondition/limitation, leaving the agent to infer the selection context.

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