com.kernelcad/kernelcad MCP server

Return the newest brush-painted review packet from a Studio session. After sharing a /p/<slug> link, the user can open it in the browser and paint marks over the 3D viewport to give visual feedback. Call this tool with the `slug` from that link to see the strokes — screenshot + mask + struck part names plus an optional one-line note and intent tags (e.g. "too thick", "missing", "wrong angle") describing WHAT is wrong — and act on the feedback. The slug is the capability: no OAuth required when passing `slug`; private projects require the owner to be signed in. Omit `slug` to fetch your own latest packet from your signed-in account (requires OAuth). By default returns short-lived signed Storage URLs for the screenshot + mask + meta.json plus the struck part names — small and context-friendly. Pass `paths_only: false` to also base64-inline the PNGs for clients that cannot fetch the signed URLs over HTTP.

Use this when the user wants to SEE or share the model — it persists the current kernelCAD model and returns a one-click link that opens it in the kernelCAD Studio web app, where the user can view and share it. Pass the full `.kcad` source you have been building as `code`. `code` is OPTIONAL: if you just called `evaluate_script` you can omit it and this reuses that last evaluated source automatically (no need to re-send the whole script). Pass `code` explicitly to override, or whenever you have not evaluated this exact source yet. The result includes a `slug` — pass that `slug` on every subsequent call to UPDATE the same project in place: the user's open Studio tab re-renders live, so they can watch the model evolve as you iterate. Omit `slug` only for a new, separate model (each omission creates a new project and link). Trigger phrases: "open it in Studio", "let me see it", "show me the model"; also call it after you finish a build, and after each meaningful revision while iterating.

Use this when you need to reopen a saved project or browse what the user has saved — it fetches a kernelCAD Studio project, or lists the signed-in user's saved projects. Pass `slug` (from a /p/<slug> link or a prior listing) to fetch that project's full .kcad source and metadata — then edit and open_in_studio with the same slug so the user's open tab updates live. Private projects require their owner's OAuth connection. OMIT `slug` to list the signed-in user's saved projects (most recently updated first); that listing mode requires the OAuth connection.

Render a project's current model server-side and return it as an inline image so you can SEE what you built. Use this after open_in_studio (or any /p/<slug> link): call with that `slug` to inspect whether the build looks right. CRITICAL — the image is rendered from the MODEL on the server; it does NOT reflect the user's Studio camera, zoom, or screen. NEVER ask the user to rotate, zoom, pan, move the camera, close a slider, or change their view to help you see — you cannot affect their screen and it cannot affect this render. To see a different angle, call this tool again with a different `view`. By DEFAULT (omit `view`, or `view:"all"`) it returns a CONTACT SHEET of all six canonical views in one labeled image — a 3×2 grid, top row [iso, front, right], bottom row [back, left, top] — so you can judge the model from every side regardless of its orientation (e.g. to find which side has the doors). Pass a single `view` (iso/front/back/left/right/top) for one large render of that angle. DETERMINISTIC: the same model + view always returns the same bytes — identical bytes are NOT a stale/lagging snapshot. If you changed the model, push it with open_in_studio FIRST, then re-render to see the change. The image is always current and never a blank capture. Colors and shading match Studio (same palette / base-material color). The slug is the capability: no OAuth for public/unlisted; private projects require the owner signed in. The PNG is base64-inlined as a real image block by default; pass `paths_only: true` for metadata only. No renderable geometry or a mesh failure → { ok: false, error, hint }, never a blank image.

Return the raw per-feature triangle mesh (positions/indices/normals) of a project's current model, by slug. For the in-chat 3D viewer widget to render geometry; delivered over the MCP Apps bridge. The slug is the capability: public/unlisted need no OAuth; private requires the owner signed in.

Return the kernelcad-authoring SKILL.md body — conventions for writing .kcad.ts scripts (imports, parameters, evaluation contract, common pitfalls). Use this tool BEFORE generating CAD code if your MCP client does not list resources. Clients that do list resources should instead read `kernelcad://skills/authoring` directly — the contents are identical. INPUT: none. OUTPUT: { uri, mimeType, text } where `text` is the SKILL.md body.

Mesh a kernelCAD .kcad.ts source server-side and return a COMPACT geometry summary — overall bounds plus, per feature, its id, kind, triangle count, and bounding box. Use this to INSPECT a model's geometry without a viewer: confirm a part is the size/shape you expect, see how many triangles each feature contributes, or check that every feature produced geometry. This runs the full server-side OCCT pipeline (the same one the Studio renderer uses), so it evaluates modern sources (assembly, path, .material, …) that the legacy client worker cannot. INPUT: `source` (required) the .kcad.ts script text; `fileName` (optional) a label for diagnostics; `params` (optional) a map of parameter-name → number overrides applied before meshing (stateless slider recompute). OUTPUT: { ok, bounds, featureCount, features: [{ id, kind, triangleCount, bbox: { min:[x,y,z], max:[x,y,z] } }], failedFeatureIds, diagnostics }. `ok` is true when every feature meshed; `failedFeatureIds` lists features that failed to compile (and `ok` is then false). Raw vertex/index/normal arrays are NEVER returned — this is a summary only. To SEE the rendered model, use open_in_studio + get_latest_render instead.

Use this when you need to run a script and check it compiles. Run a kernelCAD .kcad.ts script and report pass/fail + feature count + diagnostics. When the scene is assembly-built (assembly().part(...) → .model()/.solvedModel()), also returns a parts summary { count, names }. Pass either { file: "<path>" } or { code: "<inline source>" }. Set { dryRun: true } for fast validation while iterating: transpile + capture + capture-light checks WITHOUT OCCT lowering, DFM gates, or meshing — milliseconds instead of seconds (100x+ on boolean/fillet-heavy scripts). A dry run catches script throws, capture-time API misuse, and assembly validity-gate failures, but NOT lowering failures or dfmSpec diagnostics; it leaves the active session untouched, so finish with a full (non-dry) evaluate_script before using session-dependent tools.

Use this when you need to see exactly what changed between two script versions. Structured geometric delta between two versions of a kernelCAD script — a baseline ({ baseFile } or { baseCode }) and a revision ({ file } or { code }). Returns agent-readable JSON: per-part added/removed/renamed/changed (volume mm³ + exact bbox deltas, numbers matching inspect({ of: 'part-stats' })), total interference-volume delta with per-pair detail, mate-graph changes (added/removed/changed mates incl. type, connectors, pose, limits), and param changes (value/min/max). Single-shape scripts diff as one "(root)" pseudo-part. Use after editing a script to verify exactly what changed physically before re-rendering. Read-only — never touches the active session.

Use this when you need to read facts about a model. One reader, selected by `of`: - 'assembly' — physical assembly inventory (parts, bboxes, connectors, mates, disconnected solids). - 'robot' — URDF/SDFormat export preview (links, joints, planning groups, end-effectors, issues). - 'step' — inspect an imported STEP file. - 'shape' — volume / surfaceArea / bbox for one feature ({ feature_id? }). - 'features' — features captured by the script (kind, id, params, transforms, suppression). - 'assemblies' — assembly intent (assemblies, parts, connectors, joints). - 'topology' — canonical face names + edge count for a feature ({ feature_id? }). - 'edges' — edges of a shape with optional EdgeQuery ({ feature_id?, query? }); returns @kc[...] refs. - 'face-edges' — boundary edges of a named canonical face ({ feature_id?, face_name }). - 'faces' — faces of a shape with optional FaceQuery ({ feature_id?, query? }); returns @kc[...] refs. - 'face-labels' — user-applied labels visible in the script. - 'mates' — mates captured by the script. - 'constraints' — sketch constraints captured by the script. - 'part-stats' — bundled parts-catalog statistics. - 'bend-table' — sheet-metal bend table for a flattened pattern. - 'params' — declared model parameters. - 'part-categories' — top-level part-catalog categories available in the bundled (and configured remote) catalog. - 'part-families' — part families within a category ({ category? }); count + exemplar ids per family. All params except `of` are subject-specific and forwarded verbatim. Most subjects accept { file | code }.

Use this when you need to check a design against a rule set. One verifier, selected by `check`: - 'assembly' — mate-aware assembly validator on the active session (run evaluate_script first). - 'urdf' — structural validity of a .urdf file ({ urdf_path }). - 'dfm' — print-readiness gates declared by dfmSpec() ({ file | code }). - 'dfm-preflight' — sheet-metal flat pattern vs a job-shop's ordering rules ({ vendor, material, thicknessIn|thicknessMm, ... }). - 'swept-collision' — sweep declared joint range(s) and report colliding poses. - 'reachable' — inverse-kinematics reachability for an end-effector ({ tip_link, target_position, ... }). - 'mounting-holes' — fastened mates expose matching hole diameters on both sides. - 'load-capacity' — closed-form Euler-Bernoulli beam stress / safety-factor check ({ loads, materials, ... }). All params except `check` are check-specific and forwarded verbatim; each check fails closed on its own missing required params.

Use this when you need to trace why a feature failed. Walk the upstream chain of a failing feature. Returns the diagnostics of the requested feature plus the diagnostics of every upstream feature in topological order (the requested feature is the last entry). Per-code hints are inline on every diagnostic — call lookup_diagnostics for the full catalogue. Pass { file?, code?, feature_id? }.

Use this when you need to edit a param() default value in a kernelCAD script. Returns the modified code as text plus diagnostics from re-evaluating the result. Caller persists the new code via standard file-write tools (this tool has no side effects).

Use this when you need to insert a new feature line into a script. Insert a new feature line into a kernelCAD script before the last top-level return statement. Returns the modified code as text plus diagnostics from re-evaluating the result. Side-effect-free. Primitives that accept faceLabels (box, cylinder, extrudeRect, extrudeCircle, extrudePolygon, extrudeRoundedRect) can receive `opts.faceLabels` in the inserted code — use `lookup_api` to see `featureKindFaceLabels` for the full value schema.

Use this when you need to author a NURBS Surface into the user's .kcad.ts. One authoring path, selected by `kind`: - 'nurbs' — insert a nurbsSurface(...) / surfaceFromCurves(...) call. Pass either { controls, degree, weights?, knots?, periodic? } for direct construction, OR { section_sketch_ids } for skinning. Slice-1 limitation: weights are accepted but currently ignored (TColStd_Array2OfReal not exposed in WASM bindings); surfaces are non-rational. - 'boundary' — insert a surfaceFromBoundary([c1,c2,c3,c4], opts?) call: one NURBS face through 4 boundary Curve3D refs (bottom, right, top, left in loop order; adjacent endpoints must coincide within 1e-6 mm) via OCCT BRepOffsetAPI_MakeFilling. The returned Surface produces no Shape until you chain .thicken(t) or .toShape() (do that via add_feature on the binding name). Returns the modified code + diagnostics. Each kind fails closed on its own missing required params.

Use this when you need to author a 3D Curve3D into the user's .kcad.ts immediately before the last top-level return. One authoring path, selected by `kind`: - 'nurbs' — insert a `nurbsCurve(controlPoints, opts?)` declaration. Pass `controlPoints` as a Vec3[] (mm, at least 2 points). Optional NURBS knobs: `degree` (default 3), rational `weights`, explicit `knots`, `closed`. - 'hermite' — insert a `hermiteG2(a, b)` declaration: a quintic Hermite curve interpolating two endpoints with matching positions, tangents, and (optional) curvatures — bridges two curves with G2 continuity. Each endpoint is `{ point: Vec3, tangent: Vec3, curvature?: Vec3 }` in mm; tangent magnitude ~ chord length; curvature defaults to [0,0,0] (G1-only). The returned binding has type Curve3D (peer to Shape / Surface) — consume it via `add_variable_sweep` (spine input), `add_surface({ kind: 'boundary' })` (boundary curve), or downstream Curve3D-accepting features. Returns the modified code + diagnostics from re-evaluating. Side-effect-free. Each kind fails closed on its own missing required params.

Use this when you need to trace features from a reference photo into waypoints. Trace pixel-space features from a reference photo into normalized [0..1] waypoints the agent can map to mm via a known scale anchor and feed to path().spline / path().nurbsSegment. Three backends are dispatched behind the scenes: `opencv` (deterministic; uniform-bg silhouette only), `vision-llm` (Claude vision; named points/cluttered backgrounds; caller-supplied ANTHROPIC_API_KEY), and `hybrid` (opencv silhouette + LLM-labeled named points). Default backend is `auto` — the tool picks based on the image's corner-color stddev. Accuracy honesty: opencv contour is geometrically exact; vision-LLM is typically 5–10% off on dense landmarks. Per-feature `confidence` is reported. Caller pays for any vision-LLM API spend via their own ANTHROPIC_API_KEY. Pair with the `kernelcad-trace-from-image` skill for the conversion-to-mm pipeline.

Use this when you need to author a variable-section sweep along a spine. Insert a `variableSweep(spine, sections, opts?)` declaration into the user's .kcad.ts immediately before the last top-level return. The result is a Shape — chain `.translate(...)`, `.union(...)`, etc. via `add_feature`. `spine_binding` references an existing variable (Curve3D / Sketch / Vec3[]) in the source; each `sections[i].profile_binding` references an existing Sketch. Sections must be strictly increasing in `t` and span [0, 1]; first t=0, last t=1. Orientation is not exposed by this MCP tool until runtime orientation support is wired. Validates every binding exists in the source via regex before inserting (fast structured error vs capture-time stack). Returns the modified code + diagnostics. Side-effect-free.

Use this when you need to author text into a kernelCAD script before the last top-level return. One authoring path, selected by `mode`: - 'sketch' — insert a sketch.text(...) call. The emitted sketch is chainable: pair with subsequent .extrude(...) / cut(...) edits to land an engraved or raised text feature. - 'emboss' — insert a `<shape>.embossText({...})` chained call onto an existing Shape `target`. Use for engraved brand text on faces (Ray-Ban temple, CE mark, model number). `depth > 0` raises text out of the face; `depth < 0` engraves text into the face. Lowers via replicad drawText → sketchOnFace → extrude → fuse|cut. Default font is the runtime-bundled Liberation Sans. Side-effect-free; returns the modified code plus diagnostics from re-evaluating. Each mode fails closed on its own missing required params.

Use this when you need to wrap a 2D curve onto a 3D face. Insert a `<shape>.projectCurve({ curve, face, scaleMode?, asEdge? })` chained call into a kernelCAD script. Wraps a 2D closed curve onto a 3D face along the face normal; pair with `.extrude(d)` / `.cut(...)` for engraved logos or label inserts on curved bodies. `asEdge: true` is captured but currently deferred at lower time (BRepProj_Projection not bundled). Side-effect-free; returns modified code plus diagnostics.

Use this when you need to repeat a feature in a pattern. Insert a Shape.patternLinear / .patternCircular / .patternGrid call into a kernelCAD script before the last top-level return. Pass structured args (kind + the matching spec object). Returns the modified code plus diagnostics from re-evaluating. Side-effect-free. The pattern feature is a single editable unit; pattern-instance face refs resolve via `<sourceId>_pattern_<i>` on the pattern feature's lineage. Geometric note: pattern is implemented as cumulative boolean union of transformed source copies — additive features (boxes, ribs, fins, spokes) pattern cleanly; patterning a subtractive feature (hole, cutout) only preserves the per-instance void when adjacent bodies are disjoint.

Use this when you need to remove a feature line from a script. Remove a single line from a kernelCAD script identified by a substring match. Returns the modified code plus diagnostics from re-evaluating. Refuses to remove the line containing the return statement. Side-effect-free.

Use this when you need to resolve or inspect topology against a script's lowered geometry. Selected by `mode` (default 'evaluate'): - 'evaluate' — inspect a Query (@kc[...] ref, @kcq[...] DSL, or { ast }); returns matched entities. Pass expect:'unique' to assert exactly-one. - 'resolve' — resolve a single @kc[...] / @kcq[...] ref to one entity ({ ref }). - 'lineage' — walk the HistoryMap for a named face ref ({ feature_id, ref }). All params except `mode` are forwarded verbatim.

Use this when you need to list the kernelCAD script-runtime surface: global functions (box, path, selectEdges, helix, etc), Shape methods (fillet, sweep, lower, etc), Sketch methods (extrude, revolve, sweep), PathBuilder methods, EdgeQuery/FaceQuery key sets, and featureKindFaceLabels (which globals accept opts.faceLabels and valid value shapes). Use this to discover what is callable from a .kcad.ts script.

Use this when you need the kernelCAD 26-code diagnostic catalogue with hint templates. Tiny one-shot call; useful for an agent that wants to pre-populate retry strategies. Hints are also inline on every emitted diagnostic — this tool just gives you the canonical list up front.

Use this when you need to export geometry to a file. One exporter, selected by `target`: - target:'model' — export the script geometry to one file. Pass { file | code }, a required { output_path }, and { format }. Supported formats: stl (binary STL mesh), step (BREP CAD interchange), dxf (planar laser/waterjet profile from a Region or planar face), 3mf (slicer-friendly mesh with per-part colors), glb (web-viewer / AR with PBR materials), svg-drawing (third-angle engineering-drawing sheet: front/top/left + isometric views, hidden edges dashed, tangent edges thin, overall bounding-box dimensions, title block; assemblies are drawn with inter-part occlusion). Robot descriptions: urdf (tree-topology robot description), srdf (motion-planning semantics layered over the URDF), sdf-gazebo (SDFormat 1.10 with native ball joints, closed loops, and solved per-link poses). urdf and sdf-gazebo also write one meshes/<part>.stl per link next to output_path (reported in mesh_files) — ship the whole directory to the consumer. STL exports run a watertight verify by default; failures return ok: false with export.mesh.not-watertight (open-edge count + up to 5 crack-cluster locations) but the file is still written so the broken mesh can be inspected. Optional { feature_id } selects which feature to export (default: last). Optional { options } carries per-format options bag (see the kernelcad-mcp skill for the per-format keys: dxf layers/tolerance/unit, 3mf printUnit/embedSource, glb axis/draco). - target:'part' — export solved-assembly parts as individual binary STL files in their modeled (world-frame) positions. Pass { file | code }, plus { part, output_path } for one part or { output_dir } for all parts (files land at <output_dir>/<part>.stl). A watertight verify runs on every exported mesh by default and fails the call with export.mesh.not-watertight; unknown part names fail with export.part.not-found listing the valid names. Pass { no_verify: true } to skip the watertight gate. All params except `target` are forwarded verbatim; each target fails closed on its own missing required params.

Use this when you need a canonical pattern snippet for a CAD task. Search the kernelCAD cookbook for canonical pattern snippets. Returns top-k snippets matching the natural-language query, ranked by BM25 over title/tags/keywords/trigger. Use when you need a canonical pattern for fillet-after-subtract, non-overlapping booleans, sketch-to-extrude flows, etc. Returns empty if no snippet scores above the relevance floor — proceed without cookbook help in that case.

Use this when you need to find a part in the catalog. Discover bundled (and optionally remote) part-catalog records by fuzzy query and faceted filters. Tokens AND-combine; cross-facet filters AND-combine. Pass partsBaseUrl (or set KERNELCAD_PARTS_BASE_URL) to enable the remote tier; otherwise results are bundled-only.

Use this when you need to download a catalog part as a STEP file. Resolve an id (or single-match query) to a part record and write its STEP file to the local cache. Bundled ids resolve offline; non-bundled ids require partsBaseUrl (or KERNELCAD_PARTS_BASE_URL). Returns the cache path plus a sha256 fingerprint.

Use this when you need to solve a 2D sketch constraint set. Solve a 2D sketch constraint set. Side-effect-free: pass { entities, constraints } and receive solved entities plus the original constraints. Entities are POINT, LINE, and CIRCLE records; constraints use the kernelCAD constraint vocabulary.

Use this when you need to add a sketch constraint to a list. Append one validated sketch constraint to a constraint list. Side-effect-free: pass { constraints, constraint } and receive the updated list.

Use this when you need to add a part to an assembly. Durably insert `const <binding> = <assembly>.part(partName, shapeExpression, opts?)` before the final top-level return in a kernelCAD source string. Returns modified source plus diagnostics from re-evaluating it. Side-effect-free: caller persists the returned source.

Use this when you need to add a mate connector to a part. Durably insert `<partBinding>.connector(name, { type, origin, axis?, normal? })` before the final top-level return. Use the part binding returned by add_part. Returns modified source plus diagnostics from re-evaluation. Side-effect-free.

Use this when you need to author a mate-graph relationship into the source, selected by `relation` (default 'mate'): - 'mate' — a typed mate between two connectors ({ name, a, b, type, pose?, limitsDeg?, limitsMm? }). - 'coupling' — couple a driven mate to a source mate by ratio ({ driven, source, ratio, offset? }). - 'transmission' — a physical drive path across mates ({ name, kind, sourceMate, drivenMates, path, ... }). All durably edit source and need { code, assembly_binding }. Params other than `relation` are forwarded verbatim; each relation fails closed on its own missing required params.

Use this when you need to declare a reachability target for a connector. Durably insert `<assembly>.workspace(connectorRef, { reachable, toleranceMm? })` before the final top-level return. Workspace targets are checked by solvedModel validation/review pose-envelope gates. Returns modified source plus diagnostics from re-evaluation.

Use this when you need to set how the script returns its assembly. Replace the final top-level return statement with `return <assembly>.model();` or `return <assembly>.solvedModel(poses, options?);`. Use solvedModel for mate-authored mechanisms so FK and validation run. Returns modified source plus diagnostics from re-evaluation.

Use this when you need to solve the mate graph and get part poses. Run the v0.6 mate-graph solver on the active assembly. Returns { status, poses, iterations? } where each pose is a serialized Transform ({ translation, rotateAxis, rotateDeg }). Optional poses overrides mate pose values by mate name.

Use this when you need to review a mechanism for fitness and repair mode. Run the deterministic CAD review loop: evaluate the script, validate the assembly/mate graph, check mate connectors touch modeled material, sample declared mate limits, optionally check interferences at sampled poses, report connector workspace bounds, and return a mechanism fitness verdict for agent self-review. Fitness includes repairMode: none, local-fix, parameter-tune, or topology-redesign.

Use this when you need to run a CAD design loop over multiple attempts. Run an agent CAD design loop over one or more attempt scripts: review each attempt with review_cad, continue past functional attempts that still have unresolved review warnings, return structured repair prompts, and optionally write a Studio-compatible build record JSON for visual replay.

Use this when you need the unfolded flat pattern of a bent sheet-metal part. Return the unfolded 2D flat-pattern of a bent sheet-metal Shape as a Region (outer polyline + holes + bend lines + sketch plane). Slice 1: at most 2 bends. Pass { file } or { code }; optional { featureId } to pick a specific Shape.

Use this when you need to sample a signed-distance field at a point. Sample the signed distance from an in-script sdf.* field at a 3D point. Returns { distance, inside, aabb, kind }. Distance is in mm; negative = inside the surface, 0 = exactly on the surface, positive = outside. Use this to verify SDF composition before calling sdf.materialize (which is the expensive step). The script must bind the SdfField via sdf.bind('<name>', field) and pass that name as fieldName. Hint: pass either { file } or { code }, plus { fieldName, point: [x,y,z] }.

Use this when you need to render a script's animation timeline to a video. Capture a kernelCAD script's animationView({...}) timeline to an MP4 (ffmpeg) or a PNG frame sequence, verifying the sampled poses for part interference. FILE ONLY: pass { file } (a .kcad.ts path) — there is no { code } mode, because the capture engine renders from a file on disk (its relative lib.fromSTEP imports resolve against the script directory). MP4 by default; pass { frames_dir } to write frame-0000.png... and skip ffmpeg entirely (mutually exclusive with output_path). Animation-pose interference verification runs by default (keyframe times + segment midpoints) BEFORE any browser/ffmpeg cost; { no_verify: true } skips it and { verify_every: n } additionally samples every n-th frame time. Pass { focus } or { hide } (arrays of feature ids or assembly part names, mutually exclusive) to isolate parts in the rendered frames — same semantics as `kernelcad render --focus/--hide`; visibility is render-only and does NOT affect the pose verification. Collisions DO NOT fail the call — the artifact is still written as evidence with ok: true; read verified: false + the collisions[] array. ENVIRONMENT REQUIREMENT (identical to `kernelcad render`): capture drives a headless browser against a running studio dev server reachable at http://localhost:5173 (or the VITE_PORT override); there is no bundled-static serving mode yet, so the same dev-server precondition applies in a production MCP install. Returns { ok, output_path, frame_count, duration_ms, fps, verified, verify_skipped?, collisions: [{ t_ms, a, b, volume_mm3 }], diagnostics }.

Use this when you need to LOOK at a kernelCAD model — render its script to deterministic PNG views for visual self-check (the visual half of the evaluate → render → inspect → fix loop), with NO studio or dev server required. Pass { code } (inline source) or { file } (a .kcad.ts path), exactly one. Renders the canonical engineering views (front, right, top, iso — pass { views } for a subset, e.g. ["iso"] for fastest iteration) plus an optional { pose: "<az>,<el>" } arbitrary camera angle (degrees; az=0,el=0 is front, +az rotates CCW around +Z, +el lifts the camera). NO STUDIO / DEV-SERVER REQUIRED: a prebuilt static player (dist/headless-player) is served from an ephemeral local port automatically; a running studio dev server is used as fallback, and { base_url } forces one. The only environment dependency is playwright chromium (npx playwright install chromium). Pass { focus } or { hide } (arrays of feature ids or assembly part names, mutually exclusive) to isolate parts — same semantics as `kernelcad render --focus/--hide`. PNGs are written to { out_dir } (default: a fresh temp session directory) and returned as absolute paths with per-view camera descriptions (kernelCAD is Z-up). Mechanism truth runs first, same protocol as `kernelcad render`: a broken mechanism still renders but every tile is watermarked MECHANISM BROKEN (KERNELCAD_RENDER_STRICT=1 refuses instead); read { mechanism, mechanism_failure_codes }. The probe runs full BREP interference sweeps and can dominate latency on large assemblies — pass { no_mechanism_check: true } for fast iteration (the preview then reports mechanism: "unverified"; ignored under strict mode). Returns { ok, images: [{ name, path, description }], out_dir, bounds, mechanism, render_source, render_ms, diagnostics }. PATHS ARE LOCAL to the machine running the MCP server — local stdio clients read them directly; hosted/remote clients should use open_in_studio instead.

Use this when you need to append a curved segment to an existing PathBuilder chain on the named `chain_anchor` variable. The call is injected at the END of the chain, immediately before any `.close()`. One segment kind, selected by `kind`: - 'spline' — `.spline(points, opts?)`: interpolates through every `points` waypoint (Vec2[] mm, >= 2 entries; points[0] must match current pen position). Optional `tension`, and `startTangent`/`endTangent` 2D direction vectors that constrain the first-derivative direction at the endpoints (magnitude normalised internally). Use for organic 2D outlines (eyewear brow, ergonomic handle, sneaker midsole). - 'nurbs' — `.nurbsSegment(controlPoints, opts?)`: explicit B-spline net (Vec2[] mm, >= degree+1 entries; controlPoints[0] must match pen; pen ends at controlPoints[N-1]). Optional `degree` (default 3), rational `weights` (strictly positive), explicit `knots` (length = controlPoints.length + degree + 1). - 'hermite' — `.hermiteG2(a, b)`: each endpoint `{ point: Vec2, tangent: Vec2, curvature?: Vec2 }` in mm (a.point must match pen; pen ends at b.point). `curvature` defaults to [0,0] (G1); pass matching curvatures for G2 blends. Tangent magnitude is the first derivative (~ chord length), NOT unit length. Returns the modified code + diagnostics from re-evaluating. Side-effect-free. Each kind fails closed on its own missing required params.