R3

Read the property values of R3 components

r3_component_read

Read-onlyIdempotent

Read back what components actually hold — a material's colour and roughness, a mesh's position, which material it uses. r3_project_load gives you the names; this gives you the values behind them.

Pass SEVERAL entityRefs in one call — telling six similarly-named materials apart is the case this exists for, and it is one round trip rather than six. One component: entityRef: "mesh_cube_1" (r3_component_set's name for it) works too.

What comes back is exactly what r3_component_set takes, so read → change → write needs no translation: value components are expanded inline ({"position": {"x": 0, "y": 2, "z": 0}}), references are the target's entityRef as a string (or null when empty), and lists of references are arrays of entityRefs. Use it before any relative change ("20% brighter", "move it up by one"), and after a write to confirm what landed.

Bulk data — mesh vertex arrays and anything else megabyte-sized — is NOT returned. Every property left out is listed with the reason, so an omission is never silent.

An entityRef that does not exist is reported by name and the rest are still read. Value components (a Vector3, a Color) are not read on their own: ask for the component that owns them.

Input Schema

Name	Required	Description
`entityRef`	No	Or one component, e.g. "mesh_cube_1".
`projectId`	Yes	The project the components are in, from r3_project_create or r3_project_load.
`entityRefs`	No	Which components to read, as reported by r3_project_load: an ARRAY, e.g. ["mesh_cube_1", "material_cube_1"]. Up to 50 per call.

Output Schema

Name	Required	Description
`answer`	Yes	This answer in words: what was done, what R3 measured, decided or refused, and what to do next. The same text as the result's text block. Read it: the fields beside it are the data, this is the guidance.
`projectId`	Yes
`components`	Yes
`unreadable`	Yes
`projectName`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedOct 30, 2026

addedInput schema / properties / entityRef

Added value: +{
+  "description": "Or one component, e.g. \"mesh_cube_1\".",
+  "type": "string"
+}

changedInput schema / properties / entityRefs / description

Previous value: -"Which components to read, as reported by r3_project_load, e.g. [\"mesh_cube_1\", \"material_cube_1\"]. Up to 50 per call."New value: +"Which components to read, as reported by r3_project_load: an ARRAY, e.g. [\"mesh_cube_1\", \"material_cube_1\"]. Up to 50 per call."

changedInput schema / required

Previous value: -[
-  "projectId",
-  "entityRefs"
-]New value: +[
+  "projectId"
+]

Changed2 schema fields changedOct 15, 2026

addedOutput schema / properties / answer

Added value: +{
+  "description": "This answer in words: what was done, what R3 measured, decided or refused, and what to do next. The same text as the result's text block. Read it: the fields beside it are the data, this is the guidance.",
+  "type": "string"
+}

changedOutput schema / required

Previous value: -[
-  "projectId",
-  "projectName",
-  "components",
-  "unreadable"
-]New value: +[
+  "projectId",
+  "projectName",
+  "components",
+  "unreadable",
+  "answer"
+]

First observedOct 15, 2026

TDQS

A4.6/5.0

Behavior4/5

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

Read-only and idempotent are already covered by annotations, but the description adds real behavioural detail the annotations cannot: bulk vertex arrays are deliberately excluded and every omission is reported with a reason, and a nonexistent entityRef is reported by name while the rest still resolve. It also documents the return-value shape (expanded inline values, entityRef strings, null for empty references, arrays for reference lists). It stops short of stating pagination/ordering or how the 50-item cap failure surfaces.

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 and organised into short, scannable paragraphs, each addressing a distinct question (batching, return shape, omissions, errors). It is longer than most tool descriptions and the final note on value components could be tighter, but no paragraph is redundant.

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

Completeness5/5

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

For a read tool with an output schema and full annotation coverage, this is complete: it covers what is returned, what is intentionally withheld and how that is signalled, partial-failure behaviour, and the relationship to the write counterpart. An agent has everything needed to call it correctly and interpret the result.

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 coverage is 100%, so the baseline is 3. The description still adds genuine selection semantics beyond the schema: it tells the agent that multiple entityRefs should be preferred in one call, and that the singular entityRef form is an equivalent shorthand for a single component — a distinction the schema text alone leaves thin.

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+resource with scope: read back the values components hold (colour, roughness, position, material reference). It explicitly contrasts with r3_project_load ("gives you the names; this gives you the values behind them") and with r3_component_set, so the agent can slot it into the read/modify/write cycle 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.

Usage Guidelines5/5

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

Gives concrete when-to-use cases (use before any relative change like "20% brighter"; use after a write to confirm what landed) and an explicit batching recommendation with the scenario it serves (telling six similarly-named materials apart). It also names the sibling to use for name discovery, so alternatives and exclusions are both present.

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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