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get_usd_attribute

Read a USD attribute value from a prim, with support for long array slicing and time-sampled attributes using the current frame when no time is given.

Instructions

Read a USD attribute value from a prim.

A long array (over 16 elements) answers with value as a summary (size, element_type, head, min/max) plus slice: the elements from offset, at most limit of them (default the first 64), with has_more. Walk a big array by raising offset; pass full=True to get every element in value at once.

A time-sampled attribute (a PointInstancer's positions, protoIndices) has nothing in its default slot: read with no time it answers null. With no time given, the current frame is read instead, and the reply carries time, time_source, time_samples and time_range, so value: null never stands unexplained next to is_authored: true.

Args: node_path: LOP node path. prim_path: USD prim path. attr_name: Attribute name. time: Time code (frame number). Omitted on a time-sampled attribute, the current frame is used (the first sample outside the range). full: Return the whole array as value. offset: First element of the window for a long array. limit: Window size for a long array.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
fullNo
timeNo
limitNo
offsetNo
attr_nameYes
node_pathYes
prim_pathYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changedv2.24.1
    • addedInput schema / additionalProperties
      Added value: +false
  2. Changed3 schema fields changedv2.18.0
    • addedInput schema / properties / full
      Added value: +{
+  "default": false,
+  "title": "Full",
+  "type": "boolean"
+}
    • addedInput schema / properties / limit
      Added value: +{
+  "default": 64,
+  "title": "Limit",
+  "type": "integer"
+}
    • addedInput schema / properties / offset
      Added value: +{
+  "default": 0,
+  "title": "Offset",
+  "type": "integer"
+}
  3. First observedv0.1.0

TDQS

A4.3/5.0
Behavior4/5

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

With no annotations, the description carries the full burden and does so well: it explains the long-array response shape (value summary plus slice with has_more), the time-sampled behavior returning null with metadata (time, time_source, time_samples), so value:null is never unexplained. It omits error behavior for missing prims/attrs, which keeps it from a 5.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with the core purpose, then the response-shape and time semantics, then a standard Args listing. The dense return-format paragraph earns its space given no output schema, though it could be trimmed slightly.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 7-parameter, no-annotation, no-output-schema tool, the description covers the critical return semantics and array/time handling an agent needs. Only absent piece is what happens on error (invalid prim or attr).

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate, and its Args block documents all seven parameters including the semantics of time (first sample outside range = current frame), full, offset, and limit, plus the 64-element default window. node_path/prim_path/attr_name definitions are terse, leaving minor gaps.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource: 'Read a USD attribute value from a prim.' An agent can distinguish it from siblings like get_usd_attributes (plural listing), get_prim_intrinsics, and set_usd_attribute (write) without opening schemas.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives clear operational guidance: use offset to walk a big array, pass full=True to get everything, and omit time on a time-sampled attribute to read the current frame. It stops short of naming alternative tools or stating when-not-to-use (e.g., versus get_usd_attributes).

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

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