Create As-Built Joint

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

Beyond the annotations (non-readOnly, non-idempotent, non-destructive), the description discloses the key behavioral trait: components are not repositioned, the current pose is captured. It also discloses a type-dependent input requirement (face pair required for every joint type except rigid), which is real behavioral context. It does not mention that repeated calls will create duplicate joints, a notable gap given idempotentHint=false, nor what the tool returns.

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?

Three short sentences, front-loaded with the distinguishing behavior, then the usage rule, then the conditional input requirement. No filler or restatement of the title.

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 an 11-parameter mutation tool with no output schema, the description covers purpose, alternative, and the main conditional requirement. It stops short of describing failure modes (e.g., components not yet positioned, invalid face indices) or what the created joint looks like in the document, which would help an agent recover from errors.

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 73%, so much is already documented, but the description adds a cross-parameter rule the schema does not state: face_one/face_two are needed for every joint type except rigid. The axis/second_axis interplay is already covered in the schema's own description, so this is modest added value rather than a rewrite.

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 states a specific verb and resource ('Create a joint') plus the defining behavior ('keeps both components exactly where they are, capturing the current pose instead of enforcing a new one'). This immediately distinguishes it from add_joint even before reading either 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 gives an explicit selection rule ('Use this when the parts are already positioned correctly') and names the alternative with its contrasting behavior ('add_joint instead moves components to make the joint geometry coincident'). The condition that selects between the two siblings is fully spelled out.

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