Web Validator by DigestSEO

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generate_validation_report

Read-onlyIdempotent

Use this when HTML markup is already supplied. Combines Nu HTML validation with local CSS, SEO, accessibility-signal, and JSON-LD syntax checks. It does not fetch a webpage from base_url; use audit_public_webpage for a live URL.

Input Schema

TableJSON Schema

Name	Required	Description
`css`	No	Optional raw CSS source. Linked stylesheets are not fetched.
`html`	Yes	Raw HTML markup supplied by the user; this is not a webpage URL.
`base_url`	No	Only resolves relative links when check_links is true; it does not fetch this webpage.
`max_links`	No	Maximum links to check, from 1 to 20.
`check_links`	No	Whether to contact eligible public links found in the supplied HTML.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`error`	No
`links`	Yes
`overview`	Yes
`html_info`	Yes
`redirects`	Yes
`css_errors`	Yes
`seo_issues`	Yes
`css_checked`	Yes
`html_errors`	Yes
`broken_links`	Yes
`css_messages`	Yes
`seo_findings`	Yes
`failed_checks`	Yes
`healthy_links`	Yes
`html_messages`	Yes
`html_warnings`	Yes
`links_checked`	Yes
`schema_issues`	Yes
`seo_truncated`	Yes
`html_truncated`	Yes
`links_requested`	Yes
`schema_findings`	Yes
`schema_truncated`	Yes
`unreachable_links`	Yes
`html_total_messages`	Yes
`schema_blocks_checked`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedJul 12, 2026

changedOutput schema / properties / overview / properties / kind / enum

Previous value: -[
-  "html",
-  "css",
-  "seo",
-  "schema",
-  "links",
-  "report"
-]New value: +[
+  "html",
+  "css",
+  "seo",
+  "schema",
+  "links",
+  "report",
+  "site"
+]

Changed33 schema fields changedJul 12, 2026

addedInput schema / properties / base_url / description

Added value: +"Only resolves relative links when check_links is true; it does not fetch this webpage."

addedInput schema / properties / check_links / description

Added value: +"Whether to contact eligible public links found in the supplied HTML."

addedInput schema / properties / css / description

Added value: +"Optional raw CSS source. Linked stylesheets are not fetched."

addedInput schema / properties / html / description

Added value: +"Raw HTML markup supplied by the user; this is not a webpage URL."

addedInput schema / properties / max_links / description

Added value: +"Maximum links to check, from 1 to 20."

changedInput schema / properties / max_links / maximum
```
Previous value: -25New value: +20
```
addedOutput schema / properties / broken_links / maximum
```
Added value: +9007199254740991
```
addedOutput schema / properties / broken_links / minimum
```
Added value: +0
```
changedOutput schema / properties / broken_links / type
```
Previous value: -"number"New value: +"integer"
```
addedOutput schema / properties / css_checked
```
Added value: +{
+  "type": "boolean"
+}
```
addedOutput schema / properties / css_errors / maximum
```
Added value: +9007199254740991
```
addedOutput schema / properties / css_errors / minimum
```
Added value: +0
```
changedOutput schema / properties / css_errors / type
```
Previous value: -"number"New value: +"integer"
```

changedOutput schema / properties / failed_checks / items / enum

Previous value: -[
-  "html",
-  "css",
-  "links"
-]New value: +[
+  "fetch",
+  "html",
+  "css",
+  "links"
+]

addedOutput schema / properties / html_errors / maximum
```
Added value: +9007199254740991
```
addedOutput schema / properties / html_errors / minimum
```
Added value: +0
```
changedOutput schema / properties / html_errors / type
```
Previous value: -"number"New value: +"integer"
```
addedOutput schema / properties / html_info / maximum
```
Added value: +9007199254740991
```
addedOutput schema / properties / html_info / minimum
```
Added value: +0
```
changedOutput schema / properties / html_info / type
```
Previous value: -"number"New value: +"integer"
```
addedOutput schema / properties / html_warnings / maximum
```
Added value: +9007199254740991
```
addedOutput schema / properties / html_warnings / minimum
```
Added value: +0
```
changedOutput schema / properties / html_warnings / type
```
Previous value: -"number"New value: +"integer"
```
addedOutput schema / properties / links_checked / maximum
```
Added value: +9007199254740991
```
addedOutput schema / properties / links_checked / minimum
```
Added value: +0
```
changedOutput schema / properties / links_checked / type
```
Previous value: -"number"New value: +"integer"
```
addedOutput schema / properties / schema_issues / maximum
```
Added value: +9007199254740991
```
addedOutput schema / properties / schema_issues / minimum
```
Added value: +0
```
changedOutput schema / properties / schema_issues / type
```
Previous value: -"number"New value: +"integer"
```
addedOutput schema / properties / seo_issues / maximum
```
Added value: +9007199254740991
```
addedOutput schema / properties / seo_issues / minimum
```
Added value: +0
```
changedOutput schema / properties / seo_issues / type
```
Previous value: -"number"New value: +"integer"
```

changedOutput schema / required

Previous value: -[
-  "html_errors",
-  "css_errors",
-  "seo_issues",
-  "schema_issues",
-  "links_checked",
-  "broken_links",
-  "html_warnings",
-  "html_info",
-  "html_messages",
-  "css_messages",
-  "seo_findings",
-  "schema_findings",
-  "links",
-  "seo_truncated",
-  "schema_truncated",
-  "html_total_messages",
-  "html_truncated",
-  "schema_blocks_checked",
-  "healthy_links",
-  "redirects",
-  "unreachable_links",
-  "links_requested",
-  "failed_checks",
-  "overview"
-]New value: +[
+  "html_errors",
+  "css_errors",
+  "seo_issues",
+  "schema_issues",
+  "links_checked",
+  "broken_links",
+  "html_warnings",
+  "html_info",
+  "html_messages",
+  "css_messages",
+  "seo_findings",
+  "schema_findings",
+  "links",
+  "seo_truncated",
+  "schema_truncated",
+  "html_total_messages",
+  "html_truncated",
+  "schema_blocks_checked",
+  "healthy_links",
+  "redirects",
+  "unreachable_links",
+  "links_requested",
+  "css_checked",
+  "failed_checks",
+  "overview"
+]

Changed10 schema fields changedJul 12, 2026

addedOutput schema / properties / failed_checks

Added value: +{
+  "items": {
+    "enum": [
+      "html",
+      "css",
+      "links"
+    ],
+    "type": "string"
+  },
+  "type": "array"
+}

addedOutput schema / properties / healthy_links

Added value: +{
+  "maximum": 9007199254740991,
+  "minimum": 0,
+  "type": "integer"
+}

addedOutput schema / properties / html_total_messages

Added value: +{
+  "maximum": 9007199254740991,
+  "minimum": 0,
+  "type": "integer"
+}

addedOutput schema / properties / html_truncated
```
Added value: +{
+  "type": "boolean"
+}
```
addedOutput schema / properties / links_requested
```
Added value: +{
+  "type": "boolean"
+}
```

addedOutput schema / properties / overview

Added value: +{
+  "additionalProperties": false,
+  "properties": {
+    "counts": {
+      "items": {
+        "additionalProperties": false,
+        "properties": {
+          "key": {
+            "type": "string"
+          },
+          "label": {
+            "type": "string"
+          },
+          "tone": {
+            "enum": [
+              "error",
+              "warning",
+              "info",
+              "success"
+            ],
+            "type": "string"
+          },
+          "value": {
+            "maximum": 9007199254740991,
+            "minimum": 0,
+            "type": "integer"
+          }
+        },
+        "required": [
+          "key",
+          "label",
+          "value",
+          "tone"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "detail": {
+      "type": "string"
+    },
+    "headline": {
+      "type": "string"
+    },
+    "kind": {
+      "enum": [
+        "html",
+        "css",
+        "seo",
+        "schema",
+        "links",
+        "report"
+      ],
+      "type": "string"
+    },
+    "next_action": {
+      "type": "string"
+    },
+    "shown": {
+      "maximum": 9007199254740991,
+      "minimum": 0,
+      "type": "integer"
+    },
+    "status": {
+      "enum": [
+        "passed",
+        "needs_attention",
+        "partial",
+        "failed",
+        "not_applicable"
+      ],
+      "type": "string"
+    },
+    "title": {
+      "type": "string"
+    },
+    "total": {
+      "maximum": 9007199254740991,
+      "minimum": 0,
+      "type": "integer"
+    },
+    "truncated": {
+      "type": "boolean"
+    }
+  },
+  "required": [
+    "kind",
+    "status",
+    "title",
+    "headline",
+    "detail",
+    "total",
+    "shown",
+    "truncated",
+    "counts"
+  ],
+  "type": "object"
+}

addedOutput schema / properties / redirects

Added value: +{
+  "maximum": 9007199254740991,
+  "minimum": 0,
+  "type": "integer"
+}

addedOutput schema / properties / schema_blocks_checked

Added value: +{
+  "maximum": 9007199254740991,
+  "minimum": 0,
+  "type": "integer"
+}

addedOutput schema / properties / unreachable_links

Added value: +{
+  "maximum": 9007199254740991,
+  "minimum": 0,
+  "type": "integer"
+}

changedOutput schema / required

Previous value: -[
-  "html_errors",
-  "css_errors",
-  "seo_issues",
-  "schema_issues",
-  "links_checked",
-  "broken_links",
-  "html_warnings",
-  "html_info",
-  "html_messages",
-  "css_messages",
-  "seo_findings",
-  "schema_findings",
-  "links",
-  "seo_truncated",
-  "schema_truncated"
-]New value: +[
+  "html_errors",
+  "css_errors",
+  "seo_issues",
+  "schema_issues",
+  "links_checked",
+  "broken_links",
+  "html_warnings",
+  "html_info",
+  "html_messages",
+  "css_messages",
+  "seo_findings",
+  "schema_findings",
+  "links",
+  "seo_truncated",
+  "schema_truncated",
+  "html_total_messages",
+  "html_truncated",
+  "schema_blocks_checked",
+  "healthy_links",
+  "redirects",
+  "unreachable_links",
+  "links_requested",
+  "failed_checks",
+  "overview"
+]

Changed10 schema fields changedJul 11, 2026

addedOutput schema / properties / css_messages

Added value: +{
+  "items": {
+    "additionalProperties": false,
+    "properties": {
+      "context": {
+        "type": "string"
+      },
+      "line": {
+        "type": "number"
+      },
+      "message": {
+        "type": "string"
+      }
+    },
+    "required": [
+      "line",
+      "message"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

addedOutput schema / properties / html_info
```
Added value: +{
+  "type": "number"
+}
```

addedOutput schema / properties / html_messages

Added value: +{
+  "items": {
+    "additionalProperties": false,
+    "properties": {
+      "column": {
+        "type": "number"
+      },
+      "line": {
+        "type": "number"
+      },
+      "message": {
+        "type": "string"
+      },
+      "type": {
+        "enum": [
+          "error",
+          "warning",
+          "info"
+        ],
+        "type": "string"
+      }
+    },
+    "required": [
+      "type",
+      "message"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

addedOutput schema / properties / html_warnings
```
Added value: +{
+  "type": "number"
+}
```

addedOutput schema / properties / links

Added value: +{
+  "items": {
+    "additionalProperties": false,
+    "properties": {
+      "message": {
+        "type": "string"
+      },
+      "ok": {
+        "type": "boolean"
+      },
+      "status": {
+        "anyOf": [
+          {
+            "type": "number"
+          },
+          {
+            "enum": [
+              "blocked",
+              "failed"
+            ],
+            "type": "string"
+          }
+        ]
+      },
+      "url": {
+        "type": "string"
+      }
+    },
+    "required": [
+      "url",
+      "status",
+      "ok"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

addedOutput schema / properties / schema_findings

Added value: +{
+  "items": {
+    "additionalProperties": false,
+    "properties": {
+      "category": {
+        "enum": [
+          "SEO",
+          "Schema",
+          "Accessibility"
+        ],
+        "type": "string"
+      },
+      "message": {
+        "type": "string"
+      },
+      "severity": {
+        "enum": [
+          "error",
+          "warning",
+          "info"
+        ],
+        "type": "string"
+      }
+    },
+    "required": [
+      "severity",
+      "category",
+      "message"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

addedOutput schema / properties / schema_truncated
```
Added value: +{
+  "type": "boolean"
+}
```

addedOutput schema / properties / seo_findings

Added value: +{
+  "items": {
+    "additionalProperties": false,
+    "properties": {
+      "category": {
+        "enum": [
+          "SEO",
+          "Schema",
+          "Accessibility"
+        ],
+        "type": "string"
+      },
+      "message": {
+        "type": "string"
+      },
+      "severity": {
+        "enum": [
+          "error",
+          "warning",
+          "info"
+        ],
+        "type": "string"
+      }
+    },
+    "required": [
+      "severity",
+      "category",
+      "message"
+    ],
+    "type": "object"
+  },
+  "type": "array"
+}

addedOutput schema / properties / seo_truncated
```
Added value: +{
+  "type": "boolean"
+}
```

changedOutput schema / required

Previous value: -[
-  "html_errors",
-  "css_errors",
-  "seo_issues",
-  "schema_issues",
-  "links_checked",
-  "broken_links"
-]New value: +[
+  "html_errors",
+  "css_errors",
+  "seo_issues",
+  "schema_issues",
+  "links_checked",
+  "broken_links",
+  "html_warnings",
+  "html_info",
+  "html_messages",
+  "css_messages",
+  "seo_findings",
+  "schema_findings",
+  "links",
+  "seo_truncated",
+  "schema_truncated"
+]

First observedJul 11, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and non-destructive behavior. The description adds useful behavioral specifics: it combines Nu HTML validation with CSS, SEO, accessibility, and JSON-LD checks, and clarifies that base_url only resolves links without fetching. This adds context beyond the annotations, though it does not discuss potential rate limits or authentication, which are not covered by annotations.

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

Conciseness5/5

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

Three sentences with no filler. The first sentence establishes usage context, the second summarizes the tool's functionality, and the third provides a critical limitation and sibling alternative. Efficient and well-structured.

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 tool with a rich output schema, detailed parameter descriptions, and comprehensive annotations, the description covers the primary use case, the main limitation (no fetching), and the alternative tool. Everything an agent needs to decide whether to call this tool and what it does is present.

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 100%, so each parameter is well-documented in the schema. The description adds minimal param-specific meaning (e.g., 'local CSS' clarifies css scope, and the base_url limitation is also in the schema), but it does not compensate further. Baseline 3 is appropriate.

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 specifies a clear verb and resource: validates supplied HTML markup with multiple checks. It explicitly distinguishes itself from audit_public_webpage by stating it does not fetch a webpage from base_url, making it easy to tell apart from siblings.

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?

States the condition for use ('when HTML markup is already supplied') and explicitly says not to use it for live URLs, pointing to audit_public_webpage as the alternative. This is explicit when-to-use and when-not-to-use guidance.

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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