define_usd_prim

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

Goes well beyond the annotations (readOnlyHint=false, destructiveHint=true) by disclosing what is actually destroyed or mutated: an existing prim of another type is replaced, missing ancestors are created as typeless prims, an unknown specifier is refused before anything is authored, and a failed specifier write fails the whole call. It also flags the in-memory-only behavior and the persistence escape hatch.

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?

Dense and front-loaded: the core action and scope come first, then consequences, then alternatives, then a compact Returns block. It is information-rich rather than padded, though the sentences pack multiple clauses and could be marginally tighter.

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 a mutation tool with no output schema, the description supplies the return shape (prim_path, type_name, specifier, is_valid, specifier_set_ok, requested), the failure semantics, and the interaction with save_usd_stage. Nothing an agent needs to invoke or interpret it is 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 description coverage is 100%, so the baseline would be 3, but the description adds real semantic meaning: the default type_name is Xform and leaving it out on an existing prim retypes it, and the specifier is only reported when the write succeeded. This is more than a restatement of the schema.

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 specific verb and resource with full scope: define a prim of given type at prim_path on a registered stage, at the current edit target, creating typeless ancestors. It explicitly distinguishes itself from the sibling tools override_usd_prim (authors an over) and set_usd_prim_type (changes only the type), so an agent can route correctly without opening a 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?

Gives explicit when-to-use and when-not-to-use guidance: use override_usd_prim to author an over instead, set_usd_prim_type to change only the type, and save_usd_stage to persist since changes are in-memory only. Also states that omitting type_name intentionally retypes an existing prim to Xform, which is a non-obvious usage consequence.

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