Creating an animated creature through the asset MCP

1. Choose the input route

For a conventional model, use finding-assets.md. For a supplied reference image, first follow sculpt-from-a-reference.md: record the reference credit, inventory its recognizable regions and decide which details are geometry. Then translate that brief into a creature spec. The creature tools accept JSON, not an image, and a successful compile is not proof that the result resembles a reference.

For a thin request such as “a dragon”, call creature_guide with section: "overview" and ask the single direction question described there. Freeze one identity, one signature part, one exaggeration, the mass hierarchy, the two focal parts, the stance, the value plan and the attack before writing geometry. A specific request still needs one winner when several parts compete for attention.

2. Check the installed tools

Start the MCP session from the game root. It reads .mcp.json from the launch directory. Put the project-local directory in place before starting or restarting the server:

.threenative/creatures/

Call:

// creature_status
{}

Then call creature_guide for overview, syntax, and the stage you are entering. The guide returned by the pinned server is the authority for supported spec fields and current limits; do not copy a wolf example's coordinates or invent fields from memory.

creature_status separates the fixed compiler from optional render dependencies:

• Compiler availability is enough for a compile-only loop. It needs no Python, Chromium, account, LLM key, setup script or runtime download.
• Silhouettes need either the reported Python outline backend or the reported Chromium fallback.
• Hero images and browser claims measurement need Chromium. A missing optional dependency is an actionable unavailable result, not visual approval.

If creature_compile, creature_preview or creature_check is unavailable because the launch root has no .threenative directory, create it and restart the MCP. Keep the server's paths project-relative; never pass an absolute path, executable, URL or custom working directory.

3. Author two editable files

Keep the source of truth under .threenative/creatures/:

.threenative/creatures/wyvern.json
.threenative/creatures/wyvern-claims.json

The first file is the anyCreature spec. Use creature_guide with section: "syntax" for the complete language. At minimum, author the metre height, a nonempty palette, named joints, chains, volumes with chain and material, and all three animations. A wing or other membrane, a conspicuous jaw/horn, and an articulated tail should be authored as the parts they are, not as unrelated straight spikes. Keep the bind pose planted and include a forward- committing attack.

The claims file is also ordinary JSON and must have a nonempty claims array. Replace every placeholder with names and materials in the spec:

{
  "name": "wyvern",
  "claims": [
    {
      "type": "part_exists",
      "part": "wing_skin",
      "stage": "MID",
      "enforce": "block",
      "when": "verify"
    },
    {
      "type": "part_signature",
      "part": "wing_skin",
      "view": "side",
      "min_share": 0.12,
      "or_min_span": 0.1,
      "stage": "MID",
      "enforce": "advise",
      "when": "allocate"
    },
    {
      "type": "rig_skinned",
      "stage": "HIGH",
      "enforce": "block",
      "when": "verify"
    },
    {
      "type": "anim_named",
      "names": ["idle", "move", "attack"],
      "stage": "HIGH",
      "enforce": "block",
      "when": "verify"
    },
    {
      "type": "tri_budget",
      "min": 400,
      "max": 9000,
      "stage": "LOW",
      "enforce": "advise",
      "when": "allocate"
    }
  ]
}

Claims are measurements, not permission to skip a visual review. stage is exactly LOW, MID or HIGH; enforce is block or advise; when is allocate or verify. An unknown claim, empty stage after filtering, missing required observation or non-finite value fails closed. Use the current creature_guide claims section for the complete claim-type field list.

4. Compile into the normal asset source

Read the game's asset configuration and pass an explicit output path under its source asset directory, normally assets/creatures/. Do not put generated source in public/, and do not use the MCP's provider download directory as a creature default.

// creature_compile
{
  "specPath": ".threenative/creatures/wyvern.json",
  "outputPath": "assets/creatures/wyvern.glb"
}

The successful result is the record for this round: retain its inputSha256, outputSha256, checksSha256, measurements, clip names, diagnostics path, checks path, source snapshot path and receipt path. Read compiler diagnostics, including warnings, before deciding what to revise. The MCP validates the emitted GLB and publishes it atomically; a blocked or failed revision must not replace the last good file. When revising an existing output, pass its last known expectedOutputSha256 so a stale writer returns OUTPUT_CONFLICT instead of overwriting newer work. Edit the JSON spec, never the generated GLB.

5. Inspect, preview and review each round

After a successful compile, inspect actual bytes before judging the look:

// creature_check — structural
{
  "glbPath": "assets/creatures/wyvern.glb",
  "mode": "structural"
}

Confirm the returned measurements include reachable skin bindings, materials, bounds and clip details. A structural pass still returns visualReview: "notReviewed".

Request fresh images from the same compiled GLB:

// creature_preview — silhouettes
{
  "glbPath": "assets/creatures/wyvern.glb",
  "mode": "silhouettes"
}

For a colour/lighting view, call the same tool with "mode": "hero". The result names the backend, native view names, camera and resolution, preview ID, artifact paths and hashes. Inspect the actual images for the identity, signature part, tail, jaw/horn, planted stance and readable value hierarchy. The MCP never grades its own images: visualReview remains notReviewed.

Record one small round note beside the returned artifacts: the spec hash, GLB hash, backend, what changed, what the independent visual reviewer saw, and the next edit. Do not overwrite a previous round's receipt, claims metrics or preview. A comparison using previousPreviewId is valid only when the server reports matching backend, cameras and resolutions; a backend switch requires a new baseline.

Run claims by stage, keeping the output for each stage:

// creature_check — LOW, then MID, then HIGH
{
  "glbPath": "assets/creatures/wyvern.glb",
  "mode": "claims",
  "claimsPath": ".threenative/creatures/wyvern-claims.json",
  "stage": "HIGH"
}

Run LOW and MID while allocating big forms, then HIGH after colour and animation are authored. Treat advise as measured feedback and block as a required fix. A passing claim response is not a substitute for an independent human or host-side visual review.

6. Deliver it to the game

Delivery requires all three real clips: idle, move, and attack. HIGH must find nonempty tracks bound to the actual loaded rig, and attack must commit toward the space in front of the body. Do not rename a missing clip in the game or claim success from a spec field alone.

Use the existing asset cook and loader. The source GLB stays under assets/; let the normal build produce its cooked output, then load it through the same path as every other model. In the existing scene, use SkeletalMesh3D and AnimationPlayer (search the engine capability manifest first), set the authored body as strideRoot when the scene needs locomotion, and use the measured height rather than a universal scale workaround. Play idle -> move -> attack in the game and assert visible geometry, expected size, skin deformation, bound animation tracks and stable bone lengths on every target you claim.

The final artifact is complete only after both machine results and independent visual review are recorded. If Python or Chromium is unavailable, report a compile-only or structural result and leave preview/claims delivery outstanding; never turn an unavailable optional tool into approval. If the target is browser and native, run the same consumer scenario on both. Android and iOS stay unclaimed unless their own playtests execute.