JSON-RPC Reference

Complete specification for Fantasy402 MCP API using JSON-RPC 2.0 protocol.

Protocol Overview

The Fantasy402 MCP API uses JSON-RPC 2.0 for all communication. All requests and responses follow the JSON-RPC 2.0 specification.

Request Format

{
  "jsonrpc": "2.0",
  "id": "unique-request-id",
  "method": "tools/call",
  "params": {
    "name": "toolName",
    "arguments": {
      // Tool-specific arguments
    }
  }
}

Request Fields

Field	Type	Required	Description
jsonrpc	string	Yes	Must be "2.0"
id	string/number	Yes	Unique identifier for the request
method	string	Yes	Must be "tools/call"
params	object	Yes	Method parameters
params.name	string	Yes	Name of the MCP tool to execute
params.arguments	object	Yes	Arguments for the tool

Response Format

Success Response

{
  "jsonrpc": "2.0",
  "id": "unique-request-id",
  "result": {
    "content": [
      {
        "type": "text",
        "text": "Tool execution result"
      }
    ],
    "isError": false
  }
}

Error Response

{
  "jsonrpc": "2.0",
  "id": "unique-request-id",
  "error": {
    "code": -32601,
    "message": "Tool not found",
    "data": {
      "toolName": "unknownTool"
    }
  }
}

Error Codes

Code	Message	Description
-32700	Parse error	Invalid JSON received
-32600	Invalid Request	Request doesn't match JSON-RPC spec
-32601	Method not found	Unknown method requested
-32602	Invalid params	Invalid method parameters
-32603	Internal error	Internal server error
-32000	Server error	Tool execution failed

HTTP Transport

Endpoint

POST https://fantasy402-api-production.utahj4754.workers.dev/mcp

Headers

Content-Type: application/json
Authorization: Bearer <your-api-token>

HTTP Status Codes

Status	Meaning
200	Success
400	Bad Request (invalid JSON-RPC)
401	Unauthorized
403	Forbidden
404	Not Found
500	Internal Server Error

Authentication

All requests must include proper authentication via the Authorization header:

Authorization: Bearer eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9...

Contact your Fantasy402 representative for API credentials.

Rate Limiting

• Requests per minute: 1000
• Burst limit: 2000
• Refill rate: 16.67 tokens/ms

Rate limit headers are included in responses:

X-RateLimit-Limit: 1000
X-RateLimit-Remaining: 950
X-RateLimit-Reset: 1640995200

Examples

Successful Tool Call

Request:

{
  "jsonrpc": "2.0",
  "id": "req-123",
  "method": "tools/call",
  "params": {
    "name": "getActiveAccounts",
    "arguments": {
      "limit": 10
    }
  }
}

Response:

{
  "jsonrpc": "2.0",
  "id": "req-123",
  "result": {
    "content": [
      {
        "type": "text",
        "text": "[{\"id\":\"123\",\"balance\":1500.00,\"status\":\"active\"}]"
      }
    ],
    "isError": false
  }
}

Error Response

Request:

{
  "jsonrpc": "2.0",
  "id": "req-456",
  "method": "tools/call",
  "params": {
    "name": "unknownTool",
    "arguments": {}
  }
}

Response:

{
  "jsonrpc": "2.0",
  "id": "req-456",
  "error": {
    "code": -32601,
    "message": "Tool 'unknownTool' not found",
    "data": {
      "availableTools": ["getActiveAccounts", "getCustomerData", ...]
    }
  }
}