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Error response format

All API errors return a JSON body: 
{
  "detail": "Invalid or missing API key"
}
Validation errors include location details: 
{
  "detail": [
    {
      "loc": ["query", "fixture_id"],
      "msg": "Field required",
      "type": "missing"
    }
  ]
}

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HTTP status codes

StatusDescription
200Success
401Unauthorized — invalid or missing API key (must be valid UUID)
404Not found — resource does not exist
422Validation error — request parameters failed validation
426Upgrade required — WebSocket endpoint called via HTTP
429Rate limited — exceeded 100 requests/minute
500Internal server error

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Rate limiting

The MM API enforces 100 requests/minute per client API key. When rate limited, the API returns 429 Too Many Requests. Implement exponential backoff in your retry logic (wait 1s, 2s, 4s, etc.).

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Common errors

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Authentication (401)

Your API key is missing, invalid, or not in UUID format. 
# Correct
curl -H "X-API-Key: YOUR_API_KEY" \
  https://mmapi.55-tech.com/api/v1/me

# Wrong header name — returns 401
curl -H "Authorization: Bearer your-key" \
  https://mmapi.55-tech.com/api/v1/me

# Missing header — returns 401
curl https://mmapi.55-tech.com/api/v1/me

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Not found (404)

The requested resource doesn’t exist: 
curl -H "X-API-Key: YOUR_API_KEY" \
  https://mmapi.55-tech.com/api/v1/orders/999999
# Returns: 404

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Validation errors (422)

Required query parameters are missing or have invalid values. Check the loc field to identify the problematic parameter.

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WebSocket upgrade (426)

If you call the WebSocket endpoint via HTTP instead of upgrading to a WebSocket connection, you receive a 426 Upgrade Required.

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WebSocket errors

When subscribing to the WebSocket, these error messages may be returned:
ErrorDescription
api_key requiredNo api_key field in subscribe message
Invalid api_key formatNot a valid UUID
Invalid API keyKey not found or client inactive
Connection limit exceededAlready at 5 active connections for this key