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Render preview

render_preview

Show what a Blender scene looks like: a fast, low-cost preview render on a cloud GPU, back as an image in seconds. Typical requests: 'render this .blend', 'show me the scene', 'preview the turntable', 'I have no GPU', 'Blender is too slow on my laptop', 'Blenderでレンダリングして', 'GPUがない', 'ターンテーブル', '商品の360度動画'. Also use it after writing a bpy script, to see what it builds. Each preview returns a critic verdict (ok / check / fix) with fix code: apply the fixes and preview again before any final render. It also returns final_estimate (the same scene as a 1080p final) and quota_left_today; tell the user both before asking to go on. Prices come before rendering: final_offers give each next render's time and price, and a paid one needs the user's approval. A script that raises comes back as a failure with the line (nothing is rendered). When not to use: editing a scene open in the user's Blender belongs to a local Blender MCP, and a single still on a machine with its own NVIDIA GPU usually renders faster locally. This service is for CPU-only machines, animations, and scripts with no Blender installed. Limits: up to 1280x720; 1-4 frames tiled in one labeled image for the GPU time of one 720p frame. preset='product' | 'turntable' | 'animation' sets camera, light, backdrop and frames for that purpose. Other options are explained on each parameter: environment presets and 'compare', orbit (turntable), cameras (several named cameras), engine, transparent, asset_urls with 'polyhaven:' CC0 assets. Give the scene as scene_script (bpy code as text), scene_url (an https link to a .blend, .py or 3D file) or scene_id; reuse the returned scene_id in render_final.

Input Schema

NameRequiredDescriptionDefault
orbitNoTrue: turntable; an orbit camera circles the scene once (the scene's own camera is not used). Flat floors and walls are ignored when framing. A preview without frames shows 0/90/180/270 degrees; a final without frame_end renders the whole turn as an MP4. Best for imported models and product videos.
widthNoOutput width in pixels (previews are capped at 1280x720 keeping the aspect ratio; a final frame can have at most 1920x1080 pixels on free time, 3840x2160 on prepaid credit).
cameraNoName of the camera object to render from (default: the scene's active camera, or an automatic camera if there is none). Ignored with orbit=True; not combinable with cameras.
engineNo'' or 'cycles' (path tracing, default) | 'eevee' (real-time rasterizer: about half the per-frame cost on animations of a few dozen frames or more; each job pays about 7 s of shader compilation, so previews stay on Cycles).
framesNoPreview frames: '' = frame 1; '12' = one frame; '1,8,16,24' or '1-24' = up to 4 frames tiled in one labeled image (to judge camera motion and animation; same GPU time as one 720p frame).
heightNoOutput height in pixels (previews are capped at 1280x720 keeping the aspect ratio; a final frame can have at most 1920x1080 pixels on free time, 3840x2160 on prepaid credit).
presetNoPurpose preset: 'product' (4 studio shots at 0/90/180/270 deg on a plain backdrop; the final gives 4 PNGs at 1440x1440), 'turntable' (one full turn as an MP4, studio light, plain backdrop), 'animation' (the scene's own camera, lights and frame range; the scene is read first when the range is unknown), or '' (none). It fills what you do not pass; environment, orbit_frames, width/height and the frames still win when given.
blenderNoBlender version: '' (default: a .blend opens with the version it was saved in, other scenes with 5.0) or '5.0' / '5.2' (also '4.5', '4.2', '3.6'; a script that stops on Blender 5 because of an older API is rendered again on those automatically) to choose.
camerasNoSeveral camera object names (up to 8) rendered from the same frame in one job: the preview tiles them in one labeled sheet, the final returns one PNG/EXR per camera (camera_files maps names to files). For product shots from fixed angles. Not combinable with orbit, environment='compare' or camera.
samplesNoCycles samples per pixel (preview: up to 32, default 16; final: default 128).
scene_idNoscene_id returned by an earlier call (reuses the uploaded scene without sending it again).
scene_urlNohttps link to a .blend, a .py script or a 3D file (.glb/.gltf/.fbx/.usd/.obj/.stl/.ply/.abc); the service fetches it (e.g. the sample https://render.janction.jp/samples/cube_scene.py, or a 12-hour /upload link). A .gltf or .obj also brings its .bin / .mtl / textures from the same folder.
asset_urlsNoExtra files sent with the scene: https links (textures, glTF .bin) or 'polyhaven:<id>' CC0 assets from asset_search ('polyhaven:<id>@2k' for 2k textures). A .blend finds them through relative paths (same folder); a script through os.environ['JR_ASSETS_DIR'] or the jr_assets helpers.
environmentNoLighting preset: '' (the scene's own world), 'studio', 'sunset', 'overcast' or 'night' (bundled HDRIs; a good first render for scenes without lighting work), or 'compare' (preview only: all four in one labeled 2x2 image, to pick one).
transparentNoTrue renders on a transparent background (alpha) for product shots and overlays; png / exr / webm / gif / webp keep it, mp4 and prores cannot. The preview sheet shows it over dark grey.
orbit_framesNoNumber of frames for one full turn (default 24).
orbit_targetNoObject name or 'x,y,z' to centre the orbit on (default: the scene's main objects).
scene_scriptNoThe scene as bpy Python code (text). No file and no local Blender needed; the service runs it in Blender 5.0 (5.2 with blender='5.2'). Blender 5.0 API notes: materials are node-based, so set a colour on the Principled BSDF (mat.node_tree.nodes['Principled BSDF'].inputs['Base Color'].default_value = (r, g, b, 1)); mat.diffuse_color only affects the viewport; do not set Material.use_nodes. Animate with obj.keyframe_insert() (action.fcurves no longer exists; set bpy.context.preferences.edit.keyframe_new_interpolation_type = 'LINEAR' first for constant speed). Build the scene, camera and frame range only; leave resolution, samples and denoising to the service. Helpers: `import jr_assets`, then jr_assets.frame_camera(margin=1.1) points the camera at every object and fits them in the frame; jr_assets.import_model('<id>'), jr_assets.material('<id>') and jr_assets.world_hdri('<id>') use Poly Haven assets passed in asset_urls.
orbit_distanceNoMultiplier for the orbit camera distance (default 1.0).
orbit_elevationNoOrbit camera elevation in degrees (default 18).
environment_visibleNoFalse hides the HDRI from the camera (flat grey backdrop, HDRI lighting only).
environment_strengthNoMultiplier for the HDRI preset's brightness (default 1.0).

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedInput schema / properties / blender / description
      Previous value: -"Blender version: '' (default: a .blend opens with the version it was saved in, other scenes with 5.0) or '5.0' / '5.2' to choose."New value: +"Blender version: '' (default: a .blend opens with the version it was saved in, other scenes with 5.0) or '5.0' / '5.2' (also '4.5', '4.2', '3.6'; a script that stops on Blender 5 because of an older API is rendered again on those automatically) to choose."
  2. Changed1 schema field changed
    • changedInput schema / properties / scene_script / description
      Previous value: -"The scene as bpy Python code (text). No file and no local Blender needed; the service runs it in Blender 5.0. Blender 5.0 API notes: materials are node-based, so set a colour on the Principled BSDF (mat.node_tree.nodes['Principled BSDF'].inputs['Base Color'].default_value = (r, g, b, 1)); mat.diffuse_color only affects the viewport; do not set Material.use_nodes. Animate with obj.keyframe_insert() (action.fcurves no longer exists; set bpy.context.preferences.edit.keyframe_new_interpolation_type = 'LINEAR' first for constant speed). Build the scene, camera and frame range only; leave resolution, samples and denoising to the service. Helpers: `import jr_assets`, then jr_assets.frame_camera(margin=1.1) points the camera at every object and fits them in the frame; jr_assets.import_model('<id>'), jr_assets.material('<id>') and jr_assets.world_hdri('<id>') use Poly Haven assets passed in asset_urls."New value: +"The scene as bpy Python code (text). No file and no local Blender needed; the service runs it in Blender 5.0 (5.2 with blender='5.2'). Blender 5.0 API notes: materials are node-based, so set a colour on the Principled BSDF (mat.node_tree.nodes['Principled BSDF'].inputs['Base Color'].default_value = (r, g, b, 1)); mat.diffuse_color only affects the viewport; do not set Material.use_nodes. Animate with obj.keyframe_insert() (action.fcurves no longer exists; set bpy.context.preferences.edit.keyframe_new_interpolation_type = 'LINEAR' first for constant speed). Build the scene, camera and frame range only; leave resolution, samples and denoising to the service. Helpers: `import jr_assets`, then jr_assets.frame_camera(margin=1.1) points the camera at every object and fits them in the frame; jr_assets.import_model('<id>'), jr_assets.material('<id>') and jr_assets.world_hdri('<id>') use Poly Haven assets passed in asset_urls."
  3. Changed1 schema field changed
    • changedInput schema / properties / blender / description
      Previous value: -"Blender version: '' (5.0, default) or '5.2' when the worker has it."New value: +"Blender version: '' (default: a .blend opens with the version it was saved in, other scenes with 5.0) or '5.0' / '5.2' to choose."
  4. Changed2 schema fields changed
    • changedInput schema / properties / height / description
      Previous value: -"Output height in pixels (previews are capped at 1280x720 keeping the aspect ratio; a final frame can have at most 1920x1080 pixels)."New value: +"Output height in pixels (previews are capped at 1280x720 keeping the aspect ratio; a final frame can have at most 1920x1080 pixels on free time, 3840x2160 on prepaid credit)."
    • changedInput schema / properties / width / description
      Previous value: -"Output width in pixels (previews are capped at 1280x720 keeping the aspect ratio; a final frame can have at most 1920x1080 pixels)."New value: +"Output width in pixels (previews are capped at 1280x720 keeping the aspect ratio; a final frame can have at most 1920x1080 pixels on free time, 3840x2160 on prepaid credit)."
  5. Changed1 schema field changed
    • addedInput schema / properties / preset
      Added value: +{
      +  "default": "",
      +  "description": "Purpose preset: 'product' (4 studio shots at 0/90/180/270 deg on a plain backdrop; the final gives 4 PNGs at 1440x1440), 'turntable' (one full turn as an MP4, studio light, plain backdrop), 'animation' (the scene's own camera, lights and frame range; the scene is read first when the range is unknown), or '' (none). It fills what you do not pass; environment, orbit_frames, width/height and the frames still win when given.",
      +  "title": "Preset",
      +  "type": "string"
      +}
  6. Changed2 schema fields changed
    • changedInput schema / properties / height / description
      Previous value: -"Output height in pixels (previews are capped at 1280x720 keeping the aspect ratio; during the free beta a final frame can have at most 1920x1080 pixels)."New value: +"Output height in pixels (previews are capped at 1280x720 keeping the aspect ratio; a final frame can have at most 1920x1080 pixels)."
    • changedInput schema / properties / width / description
      Previous value: -"Output width in pixels (previews are capped at 1280x720 keeping the aspect ratio; during the free beta a final frame can have at most 1920x1080 pixels)."New value: +"Output width in pixels (previews are capped at 1280x720 keeping the aspect ratio; a final frame can have at most 1920x1080 pixels)."
  7. Changed21 schema fields changed
    • addedInput schema / properties / asset_urls / description
      Added value: +"Extra files sent with the scene: https links (textures, glTF .bin) or 'polyhaven:<id>' CC0 assets from asset_search ('polyhaven:<id>@2k' for 2k textures). A .blend finds them through relative paths (same folder); a script through os.environ['JR_ASSETS_DIR'] or the jr_assets helpers."
    • addedInput schema / properties / blender / description
      Added value: +"Blender version: '' (5.0, default) or '5.2' when the worker has it."
    • addedInput schema / properties / camera / description
      Added value: +"Name of the camera object to render from (default: the scene's active camera, or an automatic camera if there is none). Ignored with orbit=True; not combinable with cameras."
    • addedInput schema / properties / cameras / description
      Added value: +"Several camera object names (up to 8) rendered from the same frame in one job: the preview tiles them in one labeled sheet, the final returns one PNG/EXR per camera (camera_files maps names to files). For product shots from fixed angles. Not combinable with orbit, environment='compare' or camera."
    • addedInput schema / properties / engine / description
      Added value: +"'' or 'cycles' (path tracing, default) | 'eevee' (real-time rasterizer: about half the per-frame cost on animations of a few dozen frames or more; each job pays about 7 s of shader compilation, so previews stay on Cycles)."
    • addedInput schema / properties / environment / description
      Added value: +"Lighting preset: '' (the scene's own world), 'studio', 'sunset', 'overcast' or 'night' (bundled HDRIs; a good first render for scenes without lighting work), or 'compare' (preview only: all four in one labeled 2x2 image, to pick one)."
    • addedInput schema / properties / environment_strength / description
      Added value: +"Multiplier for the HDRI preset's brightness (default 1.0)."
    • addedInput schema / properties / environment_visible / description
      Added value: +"False hides the HDRI from the camera (flat grey backdrop, HDRI lighting only)."
    • addedInput schema / properties / frames / description
      Added value: +"Preview frames: '' = frame 1; '12' = one frame; '1,8,16,24' or '1-24' = up to 4 frames tiled in one labeled image (to judge camera motion and animation; same GPU time as one 720p frame)."
    • addedInput schema / properties / height / description
      Added value: +"Output height in pixels (previews are capped at 1280x720 keeping the aspect ratio; during the free beta a final frame can have at most 1920x1080 pixels)."
    • addedInput schema / properties / orbit / description
      Added value: +"True: turntable; an orbit camera circles the scene once (the scene's own camera is not used). Flat floors and walls are ignored when framing. A preview without frames shows 0/90/180/270 degrees; a final without frame_end renders the whole turn as an MP4. Best for imported models and product videos."
    • addedInput schema / properties / orbit_distance / description
      Added value: +"Multiplier for the orbit camera distance (default 1.0)."
    • addedInput schema / properties / orbit_elevation / description
      Added value: +"Orbit camera elevation in degrees (default 18)."
    • addedInput schema / properties / orbit_frames / description
      Added value: +"Number of frames for one full turn (default 24)."
    • addedInput schema / properties / orbit_target / description
      Added value: +"Object name or 'x,y,z' to centre the orbit on (default: the scene's main objects)."
    • addedInput schema / properties / samples / description
      Added value: +"Cycles samples per pixel (preview: up to 32, default 16; final: default 128)."
    • addedInput schema / properties / scene_id / description
      Added value: +"scene_id returned by an earlier call (reuses the uploaded scene without sending it again)."
    • addedInput schema / properties / scene_script / description
      Added value: +"The scene as bpy Python code (text). No file and no local Blender needed; the service runs it in Blender 5.0. Blender 5.0 API notes: materials are node-based, so set a colour on the Principled BSDF (mat.node_tree.nodes['Principled BSDF'].inputs['Base Color'].default_value = (r, g, b, 1)); mat.diffuse_color only affects the viewport; do not set Material.use_nodes. Animate with obj.keyframe_insert() (action.fcurves no longer exists; set bpy.context.preferences.edit.keyframe_new_interpolation_type = 'LINEAR' first for constant speed). Build the scene, camera and frame range only; leave resolution, samples and denoising to the service. Helpers: `import jr_assets`, then jr_assets.frame_camera(margin=1.1) points the camera at every object and fits them in the frame; jr_assets.import_model('<id>'), jr_assets.material('<id>') and jr_assets.world_hdri('<id>') use Poly Haven assets passed in asset_urls."
    • addedInput schema / properties / scene_url / description
      Added value: +"https link to a .blend, a .py script or a 3D file (.glb/.gltf/.fbx/.usd/.obj/.stl/.ply/.abc); the service fetches it (e.g. the sample https://render.janction.jp/samples/cube_scene.py, or a 12-hour /upload link). A .gltf or .obj also brings its .bin / .mtl / textures from the same folder."
    • addedInput schema / properties / transparent / description
      Added value: +"True renders on a transparent background (alpha) for product shots and overlays; png / exr / webm / gif / webp keep it, mp4 and prores cannot. The preview sheet shows it over dark grey."
    • addedInput schema / properties / width / description
      Added value: +"Output width in pixels (previews are capped at 1280x720 keeping the aspect ratio; during the free beta a final frame can have at most 1920x1080 pixels)."
  8. Changed1 schema field changed
    • addedInput schema / properties / cameras
      Added value: +{
      +  "anyOf": [
      +    {
      +      "items": {
      +        "type": "string"
      +      },
      +      "type": "array"
      +    },
      +    {
      +      "type": "null"
      +    }
      +  ],
      +  "default": null,
      +  "title": "Cameras"
      +}
  9. First observed

TDQS

A4.7/5.0
Behavior5/5

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

Annotations (readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false) only sketch the safety profile; the description adds substantial non-obvious behavior: output includes a critic verdict (ok/check/fix) with fix codes, final_estimate and quota_left_today, prices surface as final_offers before rendering, paid renders require user approval, and a raising script returns a failure with the offending line and renders nothing. The 1280x720 cap and 1-4-frame tiling are also disclosed. No contradiction with annotations.

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

Conciseness3/5

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

The purpose is correctly front-loaded, but the body is an over-stuffed run-on spanning pricing, quota, critic verdicts, usage examples, literal Japanese user utterances, limits and a parameter index, with some repetition (pricing is implied twice). The embedded multilingual utterance list consumes space without adding invocation-relevant meaning. Value density is high but trimming would clearly improve it.

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 0-required-parameter, 22-parameter tool with no output schema, the description covers everything an agent needs: the three ways to supply a scene, what the response contains (verdict, estimate, quota), pricing/approval flow, failure semantics, hard limits, and how presets interact with explicit options. Nothing material for correct invocation is left unstated.

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 already 100%, so the schema carries most parameter meaning and baseline would be 3. The description adds a consolidated index of the option families (preset values 'product'|'turntable'|'animation', environment presets including 'compare', orbit, cameras, engine, transparent, 'polyhaven:<id>' assets) and summarizes the three mutually exclusive scene inputs (scene_script / scene_url / scene_id) — useful because the schema declares no enums and allowed values live only in prose. It mostly restates schema content, though, so it does not reach a 5.

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?

Names a specific verb and resource ('Show what a Blender scene looks like: a fast, low-cost preview render on a cloud GPU, back as an image in seconds') and distinguishes itself from the sibling render_final ('apply the fixes and preview again before any final render', 'reuse the returned scene_id in render_final'). An agent can identify this tool and its relationship to other render_* tools 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 explicit use cases ('after writing a bpy script', 'render this .blend', 'I have no GPU') and an explicit 'When not to use' clause naming the alternatives (local Blender MCP for editing an open scene, local NVIDIA GPU for single stills) plus the positive selection rule ('for CPU-only machines, animations, and scripts with no Blender installed'). This is about as complete a routing guide as a description can carry.

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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