Agent skill
mcp-error-code-mapper
Map application errors to MCP error codes with proper messages, error types, and recovery suggestions.
Install this agent skill to your Project
npx add-skill https://github.com/a5c-ai/babysitter/tree/main/library/specializations/cli-mcp-development/skills/mcp-error-code-mapper
SKILL.md
MCP Error Code Mapper
Map application errors to MCP error codes with proper handling.
Capabilities
- Map errors to MCP error codes
- Create structured error responses
- Generate error documentation
- Implement error recovery hints
- Configure error serialization
- Create error handler utilities
Usage
Invoke this skill when you need to:
- Map application errors to MCP errors
- Create structured error responses
- Implement error handling for tools
- Generate error documentation
Inputs
| Parameter | Type | Required | Description |
|---|---|---|---|
| language | string | Yes | Target language |
| errors | array | Yes | Error definitions |
| includeRecovery | boolean | No | Include recovery hints |
Error Structure
{
"errors": [
{
"name": "FileNotFound",
"mcpCode": -32002,
"message": "File not found: {path}",
"recovery": "Check if the file exists and the path is correct"
},
{
"name": "InvalidInput",
"mcpCode": -32602,
"message": "Invalid input: {reason}",
"recovery": "Review the input parameters and try again"
}
]
}
Generated Patterns
TypeScript Error Mapper
import { McpError, ErrorCode } from '@modelcontextprotocol/sdk/types.js';
// Standard MCP Error Codes
export const MCP_ERROR_CODES = {
PARSE_ERROR: -32700,
INVALID_REQUEST: -32600,
METHOD_NOT_FOUND: -32601,
INVALID_PARAMS: -32602,
INTERNAL_ERROR: -32603,
// Custom codes (-32000 to -32099)
FILE_NOT_FOUND: -32001,
PERMISSION_DENIED: -32002,
RESOURCE_NOT_FOUND: -32003,
VALIDATION_ERROR: -32004,
} as const;
// Error with recovery hint
interface McpErrorWithRecovery extends McpError {
data?: {
recovery?: string;
details?: unknown;
};
}
// Error factory functions
export function fileNotFoundError(path: string): McpErrorWithRecovery {
return {
code: MCP_ERROR_CODES.FILE_NOT_FOUND,
message: `File not found: ${path}`,
data: {
recovery: 'Check if the file exists and the path is correct',
details: { path },
},
};
}
export function invalidParamsError(reason: string): McpErrorWithRecovery {
return {
code: MCP_ERROR_CODES.INVALID_PARAMS,
message: `Invalid parameters: ${reason}`,
data: {
recovery: 'Review the input parameters and try again',
},
};
}
// Error handler wrapper
export function handleToolError(error: unknown): McpErrorWithRecovery {
if (error instanceof Error) {
// Map known error types
if (error.message.includes('ENOENT')) {
return fileNotFoundError(error.message);
}
if (error.message.includes('EACCES')) {
return {
code: MCP_ERROR_CODES.PERMISSION_DENIED,
message: `Permission denied: ${error.message}`,
data: { recovery: 'Check file permissions' },
};
}
// Fallback to internal error
return {
code: MCP_ERROR_CODES.INTERNAL_ERROR,
message: error.message,
};
}
return {
code: MCP_ERROR_CODES.INTERNAL_ERROR,
message: 'An unexpected error occurred',
};
}
Python Error Mapper
from enum import IntEnum
from typing import Any, Optional
from dataclasses import dataclass
class McpErrorCode(IntEnum):
PARSE_ERROR = -32700
INVALID_REQUEST = -32600
METHOD_NOT_FOUND = -32601
INVALID_PARAMS = -32602
INTERNAL_ERROR = -32603
# Custom codes
FILE_NOT_FOUND = -32001
PERMISSION_DENIED = -32002
RESOURCE_NOT_FOUND = -32003
@dataclass
class McpError(Exception):
code: int
message: str
recovery: Optional[str] = None
details: Optional[Any] = None
def to_dict(self) -> dict:
result = {'code': self.code, 'message': self.message}
if self.recovery or self.details:
result['data'] = {}
if self.recovery:
result['data']['recovery'] = self.recovery
if self.details:
result['data']['details'] = self.details
return result
def file_not_found_error(path: str) -> McpError:
return McpError(
code=McpErrorCode.FILE_NOT_FOUND,
message=f'File not found: {path}',
recovery='Check if the file exists and the path is correct',
details={'path': path}
)
def handle_tool_error(error: Exception) -> McpError:
error_msg = str(error)
if 'FileNotFoundError' in type(error).__name__:
return file_not_found_error(error_msg)
if 'PermissionError' in type(error).__name__:
return McpError(
code=McpErrorCode.PERMISSION_DENIED,
message=f'Permission denied: {error_msg}',
recovery='Check file permissions'
)
return McpError(
code=McpErrorCode.INTERNAL_ERROR,
message=error_msg
)
Workflow
- Define errors - List application errors
- Map codes - Assign MCP error codes
- Create messages - User-friendly messages
- Add recovery - Recovery suggestions
- Generate handlers - Error handling code
- Document errors - Error documentation
Target Processes
- mcp-tool-implementation
- mcp-server-security-hardening
- error-handling-user-feedback
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