Fillet Two Entities

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

Annotations already signal that this is not read-only and not flagged destructive. The description adds useful behavioral detail: it returns information about the newly created ARC entity, and for radius=0 it returns the first source line instead. It also discloses the LINE+LINE-only limitation, which helps set expectations before invocation.

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 description is compact and front-loaded. The core purpose appears in the first sentence, followed by return behavior and a critical version constraint. Every sentence carries useful information and there is no filler.

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 a complete input schema, an output schema, annotations, and a description that states the supported entity types and return behavior, the tool definition gives an agent everything needed to invoke it correctly. No critical operational context is missing for the stated LINE+LINE scope.

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 100%, so the baseline is 3. The description adds meaning beyond the schema by explaining the return behavior for radius=0 and by indicating that handle1 and handle2 must both be lines. This gives the agent a better mental model of how the parameters relate to the operation.

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 opens with a specific verb and resource: 'Round a corner with a tangent arc.' It also distinguishes the tool from siblings like entity_chamfer by describing the geometry produced, and it clearly scopes the tool with 'V1 supports LINE+LINE only.'

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 makes the intended use clear: fillet two line entities with a tangent arc. It also gives a concrete when-not condition by stating LINE+LINE is the only supported input. It does not explicitly name alternatives such as entity_chamfer, but the use case is clear enough for an agent to select it appropriately.

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