awwwards-mcp

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verify_build

Read-only

Compare a built site against a reference URL to check section-structure and motion similarity, returning pass/warn/fail verdicts and evidence for fixes.

Instructions

Compare a built site against a reference (an Awwwards winner, a client's old site, any URL): band-structure match + motion fingerprint similarity, with a pass/warn/fail verdict and evidence lines. Band labels are #id.firstClass, so give your rebuild's sections stable ids/classes; anonymous rebuild labels (empty/body, or duplicates) fall back to tag+height matching. compact=true returns the verdict, overall and band score, band counts (matched, refOnly, buildOnly), motion score and captureStable (false when either capture moved or the two captured different heights/animation counts); omit it for evidence lines. Live reports also carry a capture: evidence line with each side's rendered height, animation count and stability, because fixed waits can sample async content at different moments; a score that moved with capture state is visible there. Closes the design loop: build → verify → fix → re-verify. Reference can be an award site found via search_sites, compared read-only via compare_sites. scene3d is a SEPARATE opt-in 3D gate: it replays a capture_scene_3d pack on the build canvas, compares cropped PNGs pixel-by-pixel and returns its own status/verdict under scene3d (with diff PNGs), keeping overall/verdict legacy semantics; the legacy pass never certifies a canvas, and without pixelThreshold + maxChangedFraction it reports metrics only (inconclusive).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "buildUrl": "<buildUrl>",
      "referenceUrl": "<referenceUrl>"
    },
    "name": "verify_build"
  }
}

Input Schema

Name	Required	Description	Default
`compact`	No	compact=true returns the verdict, overall and band score, band counts and motion score; omit for evidence lines
`domDiff`	No	body-subtree structural diff between reference and build
`scene3d`	No	opt-in visual 3D gate: replay a capture pack's checkpoints on the build canvas
`buildUrl`	Yes	URL of the build to verify
`viewport`	No	desktop = 1440x900 (default); mobile = 390x844 iPhone-class with deviceScaleFactor 3, isMobile + hasTouch	desktop
`referenceUrl`	Yes	URL of the reference site to match
`waitStrategy`	No	'load' waits for load plus settle; 'networkidle' waits for network quiet; omit to let the orchestrator use its scroll-census default

Output Schema

Name	Required	Description	Default
`bands`	No
`motion`	No
`domDiff`	No
`overall`	No
`scene3d`	No
`verdict`	No
`buildUrl`	No
`evidence`	No
`referenceUrl`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv1.18.0Nov 6, 2026

changedInput schema / properties / compact / description

Previous value: -"compact=true returns the verdict, overall and band scores, band counts and motion score; omit for evidence lines"New value: +"compact=true returns the verdict, overall and band score, band counts and motion score; omit for evidence lines"

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "additionalProperties": false,
+  "properties": {
+    "bands": {
+      "anyOf": [
+        {
+          "additionalProperties": false,
+          "properties": {
+            "buildOnly": {
+              "items": {
+                "type": "string"
+              },
+              "type": "array"
+            },
+            "diagnostics": {
+              "items": {
+                "additionalProperties": false,
+                "properties": {
+                  "backgroundChanged": {
+                    "type": [
+                      "boolean",
+                      "null"
+                    ]
+                  },
+                  "buildIndex": {
+                    "anyOf": [
+                      {
+                        "maximum": 9007199254740991,
+                        "minimum": 0,
+                        "type": "integer"
+                      },
+                      {
+                        "type": "null"
+                      }
+                    ]
+                  },
+                  "heightDeltaRatio": {
+                    "type": [
+                      "number",
+                      "null"
+                    ]
+                  },
+                  "matchReason": {
+                    "anyOf": [
+                      {
+                        "enum": [
+                          "label",
+                          "background",
+                          "height"
+                        ],
+                        "type": "string"
+                      },
+                      {
+                        "type": "null"
+                      }
+                    ]
+                  },
+                  "orderChanged": {
+                    "type": "boolean"
+                  },
+                  "referenceIndex": {
+                    "anyOf": [
+                      {
+                        "maximum": 9007199254740991,
+                        "minimum": 0,
+                        "type": "integer"
+                      },
+                      {
+                        "type": "null"
+                      }
+                    ]
+                  },
+                  "status": {
+                    "enum": [
+                      "matched",
+                      "reference-only",
+                      "build-only"
+                    ],
+                    "type": "string"
+                  }
+                },
+                "required": [
+                  "referenceIndex",
+                  "buildIndex",
+                  "status",
+                  "matchReason",
+                  "orderChanged",
+                  "heightDeltaRatio",
+                  "backgroundChanged"
+                ],
+                "type": "object"
+              },
+              "type": "array"
+            },
+            "matched": {
+              "items": {
+                "type": "string"
+              },
+              "type": "array"
+            },
+            "refOnly": {
+              "items": {
+                "type": "string"
+              },
+              "type": "array"
+            },
+            "score": {
+              "type": "number"
+            }
+          },
+          "required": [
+            "score",
+            "matched",
+            "refOnly",
+            "buildOnly",
+            "diagnostics"
+          ],
+          "type": "object"
+        },
+        {
+          "additionalProperties": false,
+          "properties": {
+            "buildOnly": {
+              "maximum": 9007199254740991,
+              "minimum": 0,
+              "type": "integer"
+            },
+            "matched": {
+              "maximum": 9007199254740991,
+              "minimum": 0,
+              "type": "integer"
+            },
+            "refOnly": {
+              "maximum": 9007199254740991,
+              "minimum": 0,
+              "type": "integer"
+            },
+            "score": {
+              "type": "number"
+            }
+          },
+          "required": [
+            "score",
+            "matched",
+            "refOnly",
+            "buildOnly"
+          ],
+          "type": "object"
+        }
+      ]
+    },
+    "buildUrl": {
+      "type": "string"
+    },
+    "domDiff": {},
+    "evidence": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "motion": {
+      "anyOf": [
+        {
+          "additionalProperties": false,
+          "properties": {
+            "acquisition": {},
+            "buildFingerprint": {
+              "type": "string"
+            },
+            "captureStable": {
+              "type": [
+                "boolean",
+                "null"
+              ]
+            },
+            "refFingerprint": {
+              "type": "string"
+            },
+            "score": {
+              "type": "number"
+            }
+          },
+          "required": [
+            "score",
+            "refFingerprint",
+            "buildFingerprint"
+          ],
+          "type": "object"
+        },
+        {
+          "additionalProperties": false,
+          "properties": {
+            "captureStable": {
+              "type": [
+                "boolean",
+                "null"
+              ]
+            },
+            "score": {
+              "type": "number"
+            }
+          },
+          "required": [
+            "score"
+          ],
+          "type": "object"
+        }
+      ]
+    },
+    "overall": {
+      "type": "number"
+    },
+    "referenceUrl": {
+      "type": "string"
+    },
+    "scene3d": {},
+    "verdict": {
+      "enum": [
+        "pass",
+        "warn",
+        "fail"
+      ],
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

Changed1 schema field changedv1.17.0Nov 3, 2026

addedInput schema / properties / scene3d

Added value: +{
+  "additionalProperties": false,
+  "description": "opt-in visual 3D gate: replay a capture pack's checkpoints on the build canvas",
+  "properties": {
+    "buildSelector": {
+      "description": "CSS selector of the build page's <canvas> to compare",
+      "maxLength": 2000,
+      "minLength": 1,
+      "type": "string"
+    },
+    "referenceCaptureId": {
+      "description": "captureId of the reference pack to replay (from a capture_page kind:\"scene\" op:\"capture\" run)",
+      "pattern": "^scene-[a-z0-9]{1,24}-[0-9a-f]{8}$",
+      "type": "string"
+    },
+    "tolerances": {
+      "additionalProperties": false,
+      "description": "Verdict inputs; supply pixelThreshold and maxChangedFraction together for a pass/fail",
+      "properties": {
+        "cameraAngleDeg": {
+          "description": "Accepted camera-angle delta in degrees; used only when the pack carries camera data",
+          "maximum": 180,
+          "minimum": 0,
+          "type": "number"
+        },
+        "maxChangedFraction": {
+          "description": "Max share of changed pixels (0..1) for a checkpoint to pass",
+          "maximum": 1,
+          "minimum": 0,
+          "type": "number"
+        },
+        "pixelThreshold": {
+          "description": "Per-channel normalized delta (0..1) above which a pixel counts as changed (default 0 while no verdict is issued)",
+          "maximum": 1,
+          "minimum": 0,
+          "type": "number"
+        }
+      },
+      "type": "object"
+    }
+  },
+  "required": [
+    "referenceCaptureId",
+    "buildSelector"
+  ],
+  "type": "object"
+}

Changed1 schema field changedv1.15.1Oct 30, 2026

addedInput schema / properties / waitStrategy / description

Added value: +"'load' waits for load plus settle; 'networkidle' waits for network quiet; omit to let the orchestrator use its scroll-census default"

Changed2 schema fields changedv1.14.0Oct 28, 2026

changedInput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

addedInput schema / properties / compact

Added value: +{
+  "description": "compact=true returns the verdict, overall and band scores, band counts and motion score; omit for evidence lines",
+  "type": "boolean"
+}

Changed1 schema field changedv1.13.0Oct 25, 2026
- removedInput schema / additionalProperties
```
Removed value: -false
```

Changed1 schema field changedv1.12.0Oct 24, 2026

addedInput schema / properties / domDiff

Added value: +{
+  "default": false,
+  "description": "body-subtree structural diff between reference and build",
+  "type": "boolean"
+}

Addedv1.9.0Oct 17, 2026

TDQS

A4.5/5.0

Behavior5/5

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

With annotations already declaring readOnly/openWorld/non-idempotent/non-destructive, the description still adds substantial behavior: what compact=true suppresses, what captureStable=false means (moved capture or mismatched heights/animation counts), the tag+height fallback for anonymous band labels, and the fact that fixed waits can sample async content inconsistently so scores that moved with capture state are visible in the capture evidence line. It also discloses that scene3d without pixelThreshold + maxChangedFraction returns metrics only (inconclusive).

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 core purpose is front-loaded, but the body is a dense run-on paragraph with stacked parentheticals and some redundancy (compact behavior is restated from the schema; scene3d is explained twice). Every sentence carries information, yet the lack of separation between the main gate, capture stability, and the 3D sub-gate makes it harder to scan than it needs to be.

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 7-parameter tool with nested objects, enums, and an output schema, the description covers the gaps that matter: the band-label contract, capture-stability caveat, fallback behavior, and the separate scene3d verdict semantics. Return-value shape is already covered by the output schema, so nothing an agent needs to call this correctly is missing.

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, but the description adds meaning the schema does not carry: band labels must be #id.firstClass and the rebuild needs stable ids/classes, otherwise anonymous labels fall back to tag+height matching. That is genuine guidance about how inputs are interpreted. The compact explanation largely duplicates the schema text rather than extending it.

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 ('Compare a built site against a reference') and enumerates the exact outputs: band-structure match, motion fingerprint similarity, pass/warn/fail verdict, evidence lines. It also explicitly separates itself from compare_sites (read-only reference comparison) and from the separate scene3d 3D gate, so an agent can route 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 Guidelines4/5

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

Gives clear context: 'Closes the design loop: build → verify → fix → re-verify', points to search_sites for finding an award reference, and names compare_sites as the read-only alternative. It also states the scene3d sub-object is a separate opt-in gate and that legacy pass never certifies a canvas, which is real when/when-not guidance. It stops short of an explicit 'do not use this tool for X' exclusion, but the routing is unambiguous.

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