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Analyze HTML and CSS

analyze_html

Read-onlyIdempotent

Use this when you need to inspect generated, offline, or test HTML that you already have. Avoid it when the source is a live URL; use analyze_site, inspect_component, or create_replication_kit.

Instructions

Use this when you need to inspect generated, offline, or test HTML that you already have. Avoid it when the source is a live URL; use analyze_site, inspect_component, or create_replication_kit. Render supplied markup and extract the same design-system data as a remote page analysis. Cost: standard. Session: renders supplied markup without navigating to a remote URL. Does not write files.

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": {
      "html": "<html>"
    },
    "name": "analyze_html"
  }
}

Input Schema

Name	Required	Description
`css`	No	Optional CSS to inject into the document.
`html`	Yes	HTML document or fragment to render.
`baseUrl`	No	Optional base URL used to resolve relative assets.
`timeoutMs`	No
`maxElements`	No	Maximum DOM elements to analyze.
`includeHidden`	No	Include elements hidden by CSS or layout.
`viewportWidth`	No	Browser viewport width in CSS pixels.
`viewportHeight`	No	Browser viewport height in CSS pixels.
`maxComponentExamples`	No	Example selectors returned for each component type.

Output Schema

Name	Required	Description	Default
`result`	Yes
`guidance`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed6 schema fields changedv0.10.1Aug 28, 2026

addedOutput schema / properties / guidance

Added value: +{
+  "additionalProperties": false,
+  "properties": {
+    "cost": {
+      "enum": [
+        "light",
+        "standard",
+        "heavy"
+      ],
+      "type": "string"
+    },
+    "nextTools": {
+      "description": "Candidate follow-ups; do not call them automatically or in parallel.",
+      "items": {
+        "enum": [
+          "analyze_site",
+          "analyze_html",
+          "inspect_component",
+          "capture_screenshot",
+          "extract_assets",
+          "extract_animations",
+          "extract_layout",
+          "clone_section",
+          "capture_interactions",
+          "extract_responsive",
+          "compare_replica",
+          "create_replication_kit",
+          "capture_motion",
+          "crawl_site"
+        ],
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "sessionPolicy": {
+      "enum": [
+        "offline-document",
+        "single-url",
+        "multi-viewport",
+        "dual-page",
+        "site-crawl"
+      ],
+      "type": "string"
+    },
+    "summary": {
+      "minLength": 1,
+      "type": "string"
+    },
+    "tool": {
+      "const": "analyze_html",
+      "type": "string"
+    },
+    "warnings": {
+      "description": "Non-fatal limitations or incomplete evidence from this run.",
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "writesFiles": {
+      "type": "boolean"
+    }
+  },
+  "required": [
+    "tool",
+    "summary",
+    "nextTools",
+    "warnings",
+    "cost",
+    "writesFiles",
+    "sessionPolicy"
+  ],
+  "type": "object"
+}

addedOutput schema / properties / result / additionalProperties
```
Added value: +{}
```

addedOutput schema / properties / result / properties

Added value: +{
+  "colors": {
+    "items": {
+      "additionalProperties": {},
+      "properties": {},
+      "type": "object"
+    },
+    "type": "array"
+  },
+  "components": {
+    "items": {
+      "additionalProperties": {},
+      "properties": {},
+      "type": "object"
+    },
+    "type": "array"
+  },
+  "metadata": {
+    "additionalProperties": {},
+    "properties": {
+      "analyzedAt": {
+        "type": "string"
+      },
+      "finalUrl": {
+        "type": "string"
+      },
+      "requestedUrl": {
+        "type": "string"
+      },
+      "title": {
+        "type": "string"
+      }
+    },
+    "required": [
+      "requestedUrl",
+      "finalUrl",
+      "title",
+      "analyzedAt"
+    ],
+    "type": "object"
+  },
+  "primitives": {
+    "additionalProperties": {},
+    "properties": {},
+    "type": "object"
+  },
+  "tokens": {
+    "items": {
+      "additionalProperties": {},
+      "properties": {},
+      "type": "object"
+    },
+    "type": "array"
+  },
+  "typography": {
+    "additionalProperties": {},
+    "properties": {},
+    "type": "object"
+  },
+  "warnings": {
+    "description": "Non-fatal limitations or incomplete evidence from this run.",
+    "items": {
+      "type": "string"
+    },
+    "type": "array"
+  }
+}

addedOutput schema / properties / result / required

Added value: +[
+  "metadata",
+  "colors",
+  "typography",
+  "components",
+  "tokens",
+  "primitives",
+  "warnings"
+]

addedOutput schema / properties / result / type
```
Added value: +"object"
```

changedOutput schema / required

Previous value: -[
-  "result"
-]New value: +[
+  "result",
+  "guidance"
+]

First observedv0.8.0Aug 3, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds useful behavioral context beyond those: it renders supplied markup without navigating to a remote URL, does not write files, and extracts the same design-system data as a remote analysis. No contradiction exists; only a bit more could be said about resource limits, but the provided behavior is sufficient.

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?

The description is front-loaded with the critical scoping and alternatives, and it remains compact for a tool with nine parameters and many siblings. There is minor redundancy ('renders supplied markup' appears twice and 'remote URL' is mentioned more than once), which prevents a perfect score.

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?

Given the nine parameters, rich schema descriptions, output schema presence, and large sibling list, the description covers what is needed: when to use it, when to avoid it, what it processes, side-effect profile, and cost. Return values are not described, but the output schema exists, so the description does not need to explain them.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is high (89%), so the schema already documents most parameters in detail. The description adds little parameter-level meaning beyond the phrase 'Render supplied markup,' which maps to the html parameter. Baseline 3 is appropriate because the schema does the heavy lifting.

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?

The description states a specific action ('inspect', 'render', 'extract design-system data') applied to a clearly defined resource: generated, offline, or test HTML the agent already has. It distinguishes from siblings by explicitly naming live-URL alternatives, so the agent can tell this tool apart without opening schemas.

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?

It gives an explicit when-to-use condition ('generated, offline, or test HTML that you already have') and an explicit when-not-to-use condition ('source is a live URL'), naming analyze_site, inspect_component, and create_replication_kit as alternatives. This is direct routing guidance with no inference required.

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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