reference-data

compute_income_tax

Read-onlyIdempotent

PAID ($0.02). Statutory income tax on a TAXABLE-income figure using the country's verified marginal bracket schedule, with full per-bracket workings, effective rate and marginal rate. You pass the amount in local currency. IMPORTANT: this is tax on taxable income, NOT net take-home pay — reliefs/allowances and social-security contributions are the caller's concern and are not applied (see the response scope_note). 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
`api_key`	No	API key (bypasses x402; metered for invoicing)
`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).
`taxable_income`	Yes	Taxable income in the country's local currency, in the schedule's own period basis (annual for most; monthly for Côte d'Ivoire, Uganda, Ethiopia, Costa Rica)

Output Schema

Name	Required	Description
`tax`	No
`basis`	No
`error`	No	Present on a free refusal or error; no charge
`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
`breakdown`	No
`no_charge`	No
`price_usd`	No
`disclaimer`	No
`how_to_pay`	No
`provenance`	No	Cited official sources behind the answer
`scope_note`	No
`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
`marginal_rate`	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
`effective_rate`	No
`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": "Income tax on taxable income with per-bracket workings",
+  "properties": {
+    "basis": {},
+    "bind_series": {},
+    "breakdown": {},
+    "country": {
+      "type": "string"
+    },
+    "disclaimer": {},
+    "effective_rate": {},
+    "error": {
+      "description": "Present on a free refusal or error; no charge"
+    },
+    "explanation": {},
+    "how_to_pay": {
+      "items": {
+        "type": "string"
+      },
+      "type": "array"
+    },
+    "http_endpoint": {
+      "type": "string"
+    },
+    "marginal_rate": {},
+    "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": {},
+    "receipt": {
+      "description": "Ed25519 answer receipt when receipt=true on a paid success"
+    },
+    "scope_note": {},
+    "status": {
+      "description": "Answer status, e.g. computed or an honest no-answer status",
+      "type": "string"
+    },
+    "tax": {},
+    "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"
+}

First observedJul 24, 2026

TDQS

A4.4/5.0

Behavior5/5

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

Annotations only cover the read-only/idempotent safety profile, and the description adds substantial context beyond that: the paid model ($0.02, x402 fallback, api_key bypass), what the optional receipt does and does not certify, and a pointer to verify_answer_receipt. These are behavioral facts an agent cannot get from structured fields.

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?

Purpose and the taxable-vs-take-home caveat are front-loaded, and the pricing banner leads. It is appropriately dense for a paid tool, though the receipt/certified-extract distinction is repeated here and again in the schema, adding some redundancy.

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?

With an output schema present, return values need not be described, and the description still covers payment, fallback auth, receipt scope, and the scope_note pointer. Nothing an agent needs to invoke this correctly is missing.

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 this is the baseline case. The description reinforces the currency/period basis for taxable_income and explains the receipt and api_key semantics, but largely restates what the schema already documents in detail.

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?

Names a specific verb-and-resource ('Statutory income tax on a TAXABLE-income figure') and scopes it precisely to the country's verified marginal bracket schedule with per-bracket workings, effective and marginal rate. This clearly separates it from siblings like compute_vat and compute_employment_cost.

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 states the boundary condition ('this is tax on taxable income, NOT net take-home pay — reliefs/allowances and social-security contributions are the caller's concern'), which is real when-to-use guidance. It also routes the free-trial user to list_series, but never names compute_employment_cost or compute_vat as the alternative for payroll/consumption taxes, so sibling disambiguation is left to inference.

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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