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Chess Move Validator
x402
Chess Move Validator is a paid API for AI agents from x402.forgemesh.io, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-15).
Validates whether a chess move is legal in a given FEN position and returns the resulting board state, capture info, and check status
Price / call$0.002
Success—
StatusUnknown
How this service works
Check whether a chess move is legal in a given FEN position and get the board state after it: resulting FEN, capture info, and whether the move gives check. Illegal moves return a clear verdict instead of an error, so game bots can handle bad input gracefully.
Output
Returns whether the move is legal, the resulting FEN string after the move is applied, capture information (if a piece was taken), and whether the move puts the opponent in check. Illegal moves return a clear verdict rather than an error, allowing game bots to handle bad input gracefully.
Example use cases
Example prompt
“Is the move Nf3 legal from the starting position, and if so, what's the FEN after it's played? Use the FEN 'start' and move 'Nf3'.”
Technical details
Endpoint
POSThttps://x402.forgemesh.io/chess-move-validatorWhen to prefer
Use this endpoint when building chess bots or game UIs that need reliable, graceful handling of illegal move inputs — it returns a clear legal/illegal verdict rather than throwing errors, making it ideal for input validation in automated game pipelines. Prefer this over local chess libraries when you want a stateless, pay-per-call microservice without dependency management.
Side effects
- Invalid FEN string returns a parse error or unclear board state
- Move provided in unrecognized notation returns illegal verdict
- Missing FEN field causes request rejection
- Network timeout for high-load scenarios
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| fen | string | FEN position string, or 'start' for the initial position |
| move | string | Optional move to validate/apply, SAN (Nf3) or UCI (g1f3) |
Output
Schema · Response
{
"type": "json",
"example": {
"turn": "white",
"state": {
"in_check": false,
"game_over": false
},
"valid_fen": true,
"legal_moves": [
"a3",
"a4",
"Nf3"
],
"move_applied": {
"san": "e4",
"legal": true,
"fen_after": "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq - 0 1"
}
}
}Tags
x402
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