Resolves a d20 ability check, skill check, attack roll, or saving throw for tabl
Resolves a d20 ability check, skill check, attack roll, or saving throw for tabletop RPGs. Rolls a d20 with an optional modifier and advantage/disadvantage, compares to a DC, and reports total, success/failure, and natural-20 / natural-1. Seedable. Use it as a d20 check resolver API for any RPG.
Answeringour last check, 2026-09-24
1 of 1checks answered this week
23 msmedian answer time
$0.005listed price per call
$0.005price it asked us
Paid test badge: not yet. The checks above are free: we call the tool without paying and read the payment request it sends back. The Verified badge needs paid calls whose answers match the promised output, and nobody can buy a badge.
Endpoint
POST https://x402.agentutility.ai/ability-check
| Category | Everything else |
|---|---|
| Provider host | x402.agentutility.ai |
| Networks | eip155:8453, solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp |
| Payment schemes | exact |
| Self-reported calls, 30 days | 2 from 1 payers (the provider's figure, not ours) |
Our checks, last 30 days
| Day | Result | HTTP | Asked | Time |
|---|---|---|---|---|
| 2026-09-24 | valid payment request | 402 | $0.005 | 23 ms |
Example input (from the provider)
{
"body": {
"advantage": true,
"dc": 15,
"modifier": 5,
"seed": 2
},
"bodyType": "json",
"method": "POST",
"type": "http"
}
Promised output schema (from the provider)
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"properties": {
"input": {
"additionalProperties": false,
"properties": {
"body": {
"properties": {
"advantage": {
"description": "Roll twice, take the higher.",
"type": "boolean"
},
"dc": {
"description": "Difficulty class to beat. Omit to just get the roll.",
"type": "number"
},
"disadvantage": {
"description": "Roll twice, take the lower.",
"type": "boolean"
},
"modifier": {
"description": "Total bonus/penalty added to the d20 (-20..40). Default 0.",
"type": "number"
},
"seed": {
"description": "Optional integer seed for a reproducible roll.",
"type": "number"
}
},
"required": []
},
"bodyType": {
"enum": [
"json",
"form-data",
"text"
],
"type": "string"
},
"method": {
"enum": [
"POST"
],
"type": "string"
},
"type": {
"const": "http",
"type": "string"
}
},
"required": [
"type",
"method",
"bodyType",
"body"
],
"type": "object"
},
"output": {
"properties": {
"example": {
"properties": {
"critical_failure": {
"type": "boolean"
},
"critical_success": {
"type": "boolean"
},
"d20_rolls": {
"items": {
"type": "integer"
},
"type": "array"
},
"dc": {
"type": "integer"
},
"mode": {
"type": "string"
},
"modifier": {
"type": "integer"
},
"natural_roll": {
"type": "integer"
},
"success": {
"type": "boolean"
},
"total": {
"type": "integer"
}
},
"type": "object"
},
"type": {
"type": "string"
}
},
"required": [
"type"
],
"type": "object"
}
},
"required": [
"input"
],
"type": "object"
}