reference-data

compute_vat

Read-onlyIdempotent

PAID ($0.01). VAT breakdown for an amount: net, tax and gross using the country's current statutory rate, including per-levy components where the rate is composite (e.g. Ghana VAT + NHIL + GETFund). mode=add treats the amount as net; mode=extract backs VAT out of a gross amount. Pass api_key if you have one (instant card checkout at /pricing); otherwise the response explains how to pay via x402. The evaluation country is free to try (see list_series). Optional receipt (boolean, default false): on a paid success, include an Ed25519 answer receipt at no extra USDC. An answer receipt is not a series certified extract (GET /v1/certified/{country}/{series} is $0.10 and is not an MCP tool) and is not legal advice. Verify with verify_answer_receipt against /certified/public-key.

Input Schema

Name	Required	Description
`mode`	No	add = amount is net (default); extract = amount is gross
`amount`	Yes	Amount in the country's own currency
`api_key`	No	API key
`country`	Yes	ISO country code
`receipt`	No	Default false. When true, a paid success includes an Ed25519 answer receipt (kind answer_receipt) at no extra USDC. Unpaid 402 and free refusals do not include one. Not a series certified extract (GET /v1/certified/{country}/{series} at $0.10; that SKU is not an MCP tool).

Output Schema

Name	Required	Description
`net`	No
`tax`	No
`rate`	No
`basis`	No
`error`	No	Present on a free refusal or error; no charge
`gross`	No
`status`	No	Answer status, e.g. computed or an honest no-answer status
`country`	No
`receipt`	No	Ed25519 answer receipt when receipt=true on a paid success
`question`	No
`workings`	No
`no_charge`	No
`price_usd`	No
`disclaimer`	No
`how_to_pay`	No
`provenance`	No	Cited official sources behind the answer
`bind_series`	No
`explanation`	No
`label_basis`	No	Inputs and the rule ids that produced the two labels
`x_next_bind`	No
`http_endpoint`	No
`coverage_label`	No	How much of the question is covered: ready = complete; partial = held with a disclosed limitation or default; gap = no number served. Rules at /label-rules
`confidence_label`	No	Evidence verdict derived from source type, verification age and the stale flag (answers: the weakest series read). Rules at /label-rules
`payment_required`	No	true when the call needs payment; how_to_pay explains x402 or card

Schema Changelog

Changes observed during successful MCP inspections.

Changed5 schema fields changedOct 17, 2026

changedInput schema / properties / receipt / description

Previous value: -"Default false. When true, a paid success includes an Ed25519 answer receipt (kind answer_receipt) at no extra USDC. Unpaid 402 and free refusals do not include one. Not a series certified extract (GET /v1/certified/{country}/{series} at $0.25; that SKU is not an MCP tool)."New value: +"Default false. When true, a paid success includes an Ed25519 answer receipt (kind answer_receipt) at no extra USDC. Unpaid 402 and free refusals do not include one. Not a series certified extract (GET /v1/certified/{country}/{series} at $0.10; that SKU is not an MCP tool)."

removedOutput schema / properties / label_basis / properties / source_type / anyOf

Removed value: -[
-  {
-    "type": "string"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / label_basis / properties / source_type / type
```
Added value: +[
+  "string",
+  "null"
+]
```
removedOutput schema / properties / label_basis / properties / verification_age_days / anyOf
```
Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]
```
addedOutput schema / properties / label_basis / properties / verification_age_days / type
```
Added value: +[
+  "number",
+  "null"
+]
```

Changed3 schema fields changedOct 13, 2026

addedOutput schema / properties / confidence_label

Added value: +{
+  "description": "Evidence verdict derived from source type, verification age and the stale flag (answers: the weakest series read). Rules at /label-rules",
+  "enum": [
+    "high",
+    "medium",
+    "low"
+  ],
+  "type": "string"
+}

addedOutput schema / properties / coverage_label

Added value: +{
+  "description": "How much of the question is covered: ready = complete; partial = held with a disclosed limitation or default; gap = no number served. Rules at /label-rules",
+  "enum": [
+    "ready",
+    "partial",
+    "gap"
+  ],
+  "type": "string"
+}

addedOutput schema / properties / label_basis

Added value: +{
+  "additionalProperties": {},
+  "description": "Inputs and the rule ids that produced the two labels",
+  "properties": {
+    "confidence_reasons": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "coverage_reasons": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "inputs": {
+      "items": {},
+      "type": "array"
+    },
+    "rules": {
+      "type": "string"
+    },
+    "rules_version": {
+      "type": "string"
+    },
+    "source_type": {
+      "anyOf": [
+        {
+          "type": "string"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "stale": {
+      "type": "boolean"
+    },
+    "verification_age_days": {
+      "anyOf": [
+        {
+          "type": "number"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    }
+  },
+  "type": "object"
+}

Changed1 schema field changedOct 12, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": {},
+  "description": "VAT breakdown",
+  "properties": {
+    "basis": {},
+    "bind_series": {},
+    "country": {
+      "type": "string"
+    },
+    "disclaimer": {},
+    "error": {
+      "description": "Present on a free refusal or error; no charge"
+    },
+    "explanation": {},
+    "gross": {},
+    "how_to_pay": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "http_endpoint": {
+      "type": "string"
+    },
+    "net": {},
+    "no_charge": {
+      "type": "boolean"
+    },
+    "payment_required": {
+      "description": "true when the call needs payment; how_to_pay explains x402 or card",
+      "type": "boolean"
+    },
+    "price_usd": {
+      "type": "number"
+    },
+    "provenance": {
+      "description": "Cited official sources behind the answer"
+    },
+    "question": {},
+    "rate": {},
+    "receipt": {
+      "description": "Ed25519 answer receipt when receipt=true on a paid success"
+    },
+    "status": {
+      "description": "Answer status, e.g. computed or an honest no-answer status",
+      "type": "string"
+    },
+    "tax": {},
+    "workings": {},
+    "x_next_bind": {}
+  },
+  "type": "object"
+}

Changed1 schema field changedSep 25, 2026

addedInput schema / properties / receipt

Added value: +{
+  "default": false,
+  "description": "Default false. When true, a paid success includes an Ed25519 answer receipt (kind answer_receipt) at no extra USDC. Unpaid 402 and free refusals do not include one. Not a series certified extract (GET /v1/certified/{country}/{series} at $0.25; that SKU is not an MCP tool).",
+  "type": "boolean"
+}

Changed1 schema field changedJul 24, 2026

changedInput schema / properties / country / enum

Previous value: -[
-  "ar",
-  "bb",
-  "bo",
-  "br",
-  "bz",
-  "cl",
-  "co",
-  "cr",
-  "do",
-  "ec",
-  "gt",
-  "hn",
-  "jm",
-  "mx",
-  "ni",
-  "pa",
-  "pe",
-  "py",
-  "sv",
-  "tt",
-  "uy"
-]New value: +[
+  "ar",
+  "bb",
+  "bo",
+  "br",
+  "bz",
+  "cl",
+  "co",
+  "cr",
+  "do",
+  "ec",
+  "gt",
+  "gy",
+  "hn",
+  "jm",
+  "mx",
+  "ni",
+  "pa",
+  "pe",
+  "py",
+  "sv",
+  "tt",
+  "uy"
+]

Changed1 schema field changedJul 24, 2026

changedInput schema / properties / country / enum

Previous value: -[
-  "ar",
-  "bo",
-  "br",
-  "cl",
-  "co",
-  "cr",
-  "do",
-  "ec",
-  "gt",
-  "hn",
-  "mx",
-  "pa",
-  "pe",
-  "py",
-  "sv",
-  "uy"
-]New value: +[
+  "ar",
+  "bb",
+  "bo",
+  "br",
+  "bz",
+  "cl",
+  "co",
+  "cr",
+  "do",
+  "ec",
+  "gt",
+  "hn",
+  "jm",
+  "mx",
+  "ni",
+  "pa",
+  "pe",
+  "py",
+  "sv",
+  "tt",
+  "uy"
+]

Changed1 schema field changedJul 20, 2026

changedInput schema / properties / country / enum

Previous value: -[
-  "ar",
-  "br",
-  "cl",
-  "co",
-  "cr",
-  "do",
-  "ec",
-  "gt",
-  "mx",
-  "pe",
-  "py",
-  "uy"
-]New value: +[
+  "ar",
+  "bo",
+  "br",
+  "cl",
+  "co",
+  "cr",
+  "do",
+  "ec",
+  "gt",
+  "hn",
+  "mx",
+  "pa",
+  "pe",
+  "py",
+  "sv",
+  "uy"
+]

AddedJul 17, 2026

TDQS

A4.4/5.0

Behavior5/5

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

Annotations cover the read-only/idempotent safety profile, but the description adds substantial behavior beyond them: exact price ($0.01), the two payment paths, what happens when unpaid, that a receipt is only on paid success, that paid refusals behave differently, and that the receipt is not a certified extract nor legal advice. These are exactly the kind of non-obvious traits an agent needs.

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-loaded with the core purpose before payment mechanics and disclaimers. It is on the longer side and duplicates receipt details that also appear in the schema description, but nearly every sentence carries distinct information (pricing, payment flow, free-trial country, verification tool).

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?

Output schema exists, so return values need not be explained, and the description still covers payment behavior, receipt semantics, the certified-extract distinction, the free evaluation tier, and the companion verify_answer_receipt tool. An agent has everything needed to invoke and interpret this correctly.

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 coverage is 100%, so the schema already documents mode, amount, country, api_key, and receipt semantics. The description largely restates these (mode add/extract, receipt default false) rather than adding new format or constraint detail, so the 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?

States a specific verb and resource ('VAT breakdown for an amount: net, tax and gross') and defines the calculation basis ('country's current statutory rate'), including composite-rate handling (Ghana VAT + NHIL + GETFund). This is clearly distinct from sibling tools like compute_income_tax and compute_employment_cost without needing to name them.

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?

Gives explicit mode-selection guidance ('mode=add treats the amount as net; mode=extract backs VAT out of a gross amount') and explains the payment path (api_key vs x402). It also notes the evaluation country is free to try. It stops short of contrasting against sibling tax-computation tools, so it earns a 4 rather than a 5.

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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