Web Validator by DigestSEO

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Generate a validation report

report.validation

Read-onlyIdempotent

Validates HTML/CSS against W3C standards, audits SEO and accessibility, checks JSON-LD syntax and public links, and produces a Markdown plus structured report.

Instructions

Combines W3C HTML/CSS validation, local SEO/accessibility checks, JSON-LD syntax checks, and a bounded public-link check into a Markdown and structured report.

Input Schema

TableJSON Schema

Name	Required	Description
`baseUrl`	No	Optional public HTTP(S) base URL used to resolve relative links.
`cssFilePath`	No	Optional absolute or workspace-relative CSS file path.
`htmlFilePath`	Yes	Absolute or workspace-relative HTML or .xhtml file path.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`links`	Yes
`errors`	No
`report`	Yes
`summary`	Yes
`seoIssues`	Yes
`cssMessages`	Yes
`cssTruncated`	Yes
`failedChecks`	Yes
`htmlMessages`	Yes
`schemaIssues`	Yes
`seoTruncated`	Yes
`htmlTruncated`	Yes
`seoTotalIssues`	Yes
`schemaTruncated`	Yes
`cssTotalMessages`	Yes
`htmlTotalMessages`	Yes
`schemaTotalIssues`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv1.3.40Sep 24, 2026

changedInput schema / properties / htmlFilePath / description

Previous value: -"Absolute or workspace-relative HTML file path."New value: +"Absolute or workspace-relative HTML or .xhtml file path."

addedOutput schema / properties / summary / properties / cssWarnings

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

Changed17 schema fields changedv1.3.28Sep 23, 2026

addedOutput schema / properties / cssMessages / items / properties / compatibility

Added value: +{
+  "const": "known-validator-limitation",
+  "type": "string"
+}

addedOutput schema / properties / cssTotalMessages

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

addedOutput schema / properties / cssTruncated
```
Added value: +{
+  "type": "boolean"
+}
```
addedOutput schema / properties / htmlMessages / items / properties / subType
```
Added value: +{
+  "type": "string"
+}
```

addedOutput schema / properties / htmlTotalMessages

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

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

addedOutput schema / properties / schemaIssues / items / properties / code

Added value: +{
+  "description": "Stable machine-readable audit rule identifier.",
+  "type": "string"
+}

changedOutput schema / properties / schemaIssues / items / required

Previous value: -[
-  "severity",
-  "category",
-  "message"
-]New value: +[
+  "code",
+  "severity",
+  "category",
+  "message"
+]

addedOutput schema / properties / schemaTotalIssues

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

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

addedOutput schema / properties / seoIssues / items / properties / code

Added value: +{
+  "description": "Stable machine-readable audit rule identifier.",
+  "type": "string"
+}

changedOutput schema / properties / seoIssues / items / required

Previous value: -[
-  "severity",
-  "category",
-  "message"
-]New value: +[
+  "code",
+  "severity",
+  "category",
+  "message"
+]

addedOutput schema / properties / seoTotalIssues

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

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

addedOutput schema / properties / summary / properties / cssCompatibilityLimitations

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

changedOutput schema / properties / summary / required

Previous value: -[
-  "overallScore",
-  "htmlScore",
-  "cssScore",
-  "seoScore",
-  "linkScore",
-  "htmlErrors",
-  "htmlWarnings",
-  "cssErrors",
-  "seoErrors",
-  "seoWarnings",
-  "schemaErrors",
-  "linksChecked",
-  "brokenLinks"
-]New value: +[
+  "overallScore",
+  "htmlScore",
+  "cssScore",
+  "seoScore",
+  "linkScore",
+  "htmlErrors",
+  "htmlWarnings",
+  "cssErrors",
+  "cssCompatibilityLimitations",
+  "seoErrors",
+  "seoWarnings",
+  "schemaErrors",
+  "linksChecked",
+  "brokenLinks"
+]

changedOutput schema / required

Previous value: -[
-  "report",
-  "summary",
-  "htmlMessages",
-  "cssMessages",
-  "seoIssues",
-  "schemaIssues",
-  "links",
-  "failedChecks"
-]New value: +[
+  "report",
+  "summary",
+  "htmlMessages",
+  "htmlTotalMessages",
+  "htmlTruncated",
+  "cssMessages",
+  "cssTotalMessages",
+  "cssTruncated",
+  "seoIssues",
+  "seoTotalIssues",
+  "seoTruncated",
+  "schemaIssues",
+  "schemaTotalIssues",
+  "schemaTruncated",
+  "links",
+  "failedChecks"
+]

Addedv1.1.0Aug 29, 2026

TDQS

A4/5.0

Behavior4/5

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

Annotations already provide readOnly, openWorld, idempotent, and non-destructive hints, so the description's burden is lighter. It adds meaningful behavior: it performs combined W3C/local/JSON-LD/public-link checks and produces both Markdown and structured output. The 'bounded public-link check' clue also hints at external network behavior without contradicting the 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?

One dense, front-loaded sentence communicates the tool's purpose, scope, and output format with no filler. Every part of the sentence adds useful information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For an aggregate validation tool with a rich output schema and strong annotations, the description is largely complete. The main gap is optional-parameter behavior: an agent cannot tell from the description how omitting cssFilePath or baseUrl affects which checks run, nor exactly what 'bounded' means for the public-link check.

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 the baseline is 3. The description's check categories map loosely to the parameters, but it adds no explicit detail about whether cssFilePath gates CSS validation or whether baseUrl gates the public-link check. The schema itself already carries the parameter meaning.

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 verb and resource: it combines validations 'into a Markdown and structured report.' It enumerates the exact check categories, which clearly distinguishes this aggregate tool from single-purpose siblings like html.local, css.local, links.broken, schema.markup, and seo.metadata.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

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

The description implies this is the all-in-one validation tool, but it never explicitly says when to prefer report.validation over the individual sibling tools or when not to use it. The aggregation language gives useful context, but the agent must infer the tool-selection logic.

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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