UK Legal Research

Check MTD VAT Status

hmrc_check_mtd_status

Read-onlyIdempotent

USE THIS TOOL WHEN you have a 9-digit VAT Registration Number and need that business's Making Tax Digital VAT mandate status.

Returns whether the business is mandated for MTD, effective date, and trading name.

Connects to the HMRC sandbox by default. Set HMRC_API_BASE to 'https://api.service.hmrc.gov.uk' for production. Requires HMRC_CLIENT_ID + HMRC_CLIENT_SECRET environment variables (OAuth 2.0). Raises if credentials are not configured — do not infer status.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`vrn`	Yes	VAT Registration Number: 9 digits, e.g. '123456789'. GB prefix accepted and stripped automatically.

Output Schema

TableJSON Schema

Name	Required	Description
`vrn`	Yes	VAT Registration Number queried
`mandated`	Yes	Whether this business is mandated for MTD VAT
`trading_name`	No	Registered trading name if available
`effective_date`	No	Date from which MTD obligation applies

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedJun 14, 2026

removedInput schema / properties / params

Removed value: -{
-  "additionalProperties": false,
-  "description": "HMRCMTDStatusInput.",
-  "properties": {
-    "vrn": {
-      "description": "VAT Registration Number: 9 digits, e.g. '123456789'. GB prefix accepted and stripped automatically.",
-      "maxLength": 12,
-      "minLength": 9,
-      "type": "string"
-    }
-  },
-  "required": [
-    "vrn"
-  ],
-  "type": "object"
-}

addedInput schema / properties / vrn

Added value: +{
+  "description": "VAT Registration Number: 9 digits, e.g. '123456789'. GB prefix accepted and stripped automatically.",
+  "maxLength": 12,
+  "minLength": 9,
+  "type": "string"
+}

changedInput schema / required

Previous value: -[
-  "params"
-]New value: +[
+  "vrn"
+]

Changed1 schema field changedMay 30, 2026

changedInput schema / properties / params / description

Previous value: -"HMRCMTDStatusInput with the 9-digit VAT Registration Number."New value: +"HMRCMTDStatusInput."

Changed1 schema field changedApr 20, 2026
- addedInput schema / properties / params / description
```
Added value: +"HMRCMTDStatusInput with the 9-digit VAT Registration Number."
```

Changed8 schema fields changedApr 15, 2026

changedOutput schema / description

Previous value: -"Generic wrapper for non-object return types."New value: +"Making Tax Digital VAT status for a VAT registration number."

addedOutput schema / properties / effective_date

Added value: +{
+  "anyOf": [
+    {
+      "format": "date",
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Date from which MTD obligation applies"
+}

addedOutput schema / properties / mandated

Added value: +{
+  "description": "Whether this business is mandated for MTD VAT",
+  "type": "boolean"
+}

removedOutput schema / properties / result

Removed value: -{
-  "type": "string"
-}

addedOutput schema / properties / trading_name

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Registered trading name if available"
+}

addedOutput schema / properties / vrn

Added value: +{
+  "description": "VAT Registration Number queried",
+  "type": "string"
+}

changedOutput schema / required

Previous value: -[
-  "result"
-]New value: +[
+  "vrn",
+  "mandated"
+]

removedOutput schema / x-fastmcp-wrap-result
```
Removed value: -true
```

First observedApr 14, 2026

TDQS

A4.4/5.0

Behavior5/5

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

Annotations already mark the tool as readOnly and idempotent, and the description adds valuable behavioral context: default sandbox connection, production override via HMRC_API_BASE, required OAuth credentials, and that it raises if credentials are missing. This goes beyond the structured fields without contradicting them.

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 concise and front-loaded with the core purpose, followed by return details and environment notes. Every sentence provides value, though the environment configuration section could be trimmed without losing clarity.

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 tool's simplicity, the description covers the main use case, return fields, environment defaults, and error behavior. The presence of an output schema further reduces the need to explain return format, making this complete.

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?

The schema fully describes the only parameter (vrn) with format and example, and the description does not add new parameter information. With schema coverage at 100%, the baseline of 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 states a specific action and resource: 'USE THIS TOOL WHEN you have a 9-digit VAT Registration Number and need that business's Making Tax Digital VAT mandate status.' It clearly explains the return value (mandated status, effective date, trading name) and distinguishes from other HMRC tools like hmrc_get_vat_rate.

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?

The description provides an explicit trigger: 'USE THIS TOOL WHEN you have a 9-digit VAT Registration Number and need that business's Making Tax Digital VAT mandate status.' It also gives environment setup and warns against inferring status without credentials, though it does not name alternative tools for when-not-to-use.

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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