mcp-vdd

Validate Impact

vdd_validate

Idempotent

Validate the complete VDD chain for bidirectional traceability, drift and orphan detection, uncovered vision goals, impact metrics, and S&T assumption checks.

Instructions

VDD Phase 8: Validate the full chain — bidirectional traceability matrix, drift detection, orphan detection, uncovered vision goals, impact metrics vs targets, and 28 S&T assumption checks across 7 gates. Writes vdd/impact-report.generated.md and never overwrites a hand-authored vdd/impact-report.md. Run after implementation is complete; for the traceability matrix or per-feature spec metrics use vdd_inspect. Parameter relationships: feature narrows the check to one spec; artifactFiles maps artifact path to content for serverless runs and is omitted when resolving against a local projectRoot.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`feature`	No	Feature name: the vdd/specs/<feature>/ directory, kebab-case (e.g., "user-auth"); must reference a directory created earlier by vdd_specify
`projectRoot`	No	Project root: directory that constitution.md and the vdd/ folder are written to and resolved against. Relative paths resolve from the current working directory; keep the same value across every phase (default ".")	.
`artifactFiles`	No	Map of vdd/-relative artifact path → full file text, for serverless validate/drift detection where the tool cannot read the filesystem

Output Schema

TableJSON Schema

Name	Required	Description
`_sdt`	Yes	Strategy-and-Tactic instructions for the next step
`error`	No	Error message when the phase fails
`_phase`	Yes	VDD phase that produced this result
`output`	No	Additional structured phase output
`success`	Yes	Whether the phase completed successfully
`artifact`	No	Primary artifact produced or returned
`gateResult`	No	Quality-gate result, when the phase runs a gate

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedv1.9.0Oct 2, 2026

changedInput schema / properties / artifactFiles / description

Previous value: -"Map of artifact path → content for serverless validate/drift detection"New value: +"Map of vdd/-relative artifact path → full file text, for serverless validate/drift detection where the tool cannot read the filesystem"

changedInput schema / properties / feature / description

Previous value: -"Feature name (spec directory name)"New value: +"Feature name: the vdd/specs/<feature>/ directory, kebab-case (e.g., \"user-auth\"); must reference a directory created earlier by vdd_specify"

changedInput schema / properties / projectRoot / description

Previous value: -"Project root: directory that constitution.md and the vdd/ folder are written to and resolved against (default \".\")"New value: +"Project root: directory that constitution.md and the vdd/ folder are written to and resolved against. Relative paths resolve from the current working directory; keep the same value across every phase (default \".\")"

Changed1 schema field changedv0.1.3Sep 24, 2026

changedInput schema / properties / projectRoot / description

Previous value: -"Path to project root directory"New value: +"Project root: directory that constitution.md and the vdd/ folder are written to and resolved against (default \".\")"

Changed1 schema field changedv0.1.2Sep 24, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "https://json-schema.org/draft/2020-12/schema",
+  "additionalProperties": false,
+  "properties": {
+    "_phase": {
+      "description": "VDD phase that produced this result",
+      "type": "string"
+    },
+    "_sdt": {
+      "description": "Strategy-and-Tactic instructions for the next step",
+      "type": "string"
+    },
+    "artifact": {
+      "description": "Primary artifact produced or returned",
+      "type": "string"
+    },
+    "error": {
+      "description": "Error message when the phase fails",
+      "type": "string"
+    },
+    "gateResult": {
+      "additionalProperties": false,
+      "description": "Quality-gate result, when the phase runs a gate",
+      "properties": {
+        "checks": {
+          "description": "Number of checks run",
+          "type": "number"
+        },
+        "passed": {
+          "description": "Whether the quality gate passed",
+          "type": "boolean"
+        },
+        "total": {
+          "description": "Total number of checks",
+          "type": "number"
+        }
+      },
+      "required": [
+        "passed",
+        "checks",
+        "total"
+      ],
+      "type": "object"
+    },
+    "output": {
+      "additionalProperties": {},
+      "description": "Additional structured phase output",
+      "propertyNames": {
+        "type": "string"
+      },
+      "type": "object"
+    },
+    "success": {
+      "description": "Whether the phase completed successfully",
+      "type": "boolean"
+    }
+  },
+  "required": [
+    "success",
+    "_phase",
+    "_sdt"
+  ],
+  "type": "object"
+}

First observedv0.1.0Sep 24, 2026

TDQS

A4.5/5.0

Behavior5/5

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

Annotations only cover idempotency, openWorld and destructiveness; the description adds the concrete write behavior (writes vdd/impact-report.generated.md) and a non-obvious safety guarantee (never overwrites a hand-authored vdd/impact-report.md). This is exactly the side-effect and overwrite context an agent needs beyond the structured hints.

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?

Front-loads the phase and scope, then the write behavior and alternatives, then a compact parameter-relationships sentence. It is dense and slightly run-on in the enumerated check list, but every sentence carries actionable 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?

With an output schema present, return values need not be explained, and the description covers scope, side effects, alternatives, and parameter interplay. Coverage is strong; only the traceability-matrix-vs-vdd_inspect boundary is left mildly ambiguous.

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 already 100%, so baseline would be 3; the description goes further by explaining the relationships (feature narrows the check to a single spec; artifactFiles maps path→content for serverless runs and is omitted when resolving against a local projectRoot). That adds semantic meaning about when each parameter matters.

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 (validate) plus the exact scope of the chain being validated (traceability matrix, drift, orphans, uncovered goals, impact metrics, assumption checks across 7 gates). It also names the sibling vdd_inspect to distinguish standalone traceability/metrics work, so an agent can separate it from siblings 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 Guidelines4/5

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

Explicitly says to run it after implementation is complete and redirects the traceability matrix / per-feature metrics case to vdd_inspect. The when-to-use and the alternative are both present, though the line listing 'bidirectional traceability matrix' as part of validate while also routing 'the traceability matrix' to vdd_inspect slightly muddies the boundary.

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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