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Error codes

MCP Server Fuzzer surfaces every user-facing failure through numbered error codes. Each code follows the CCTTT format:

  • CC (two digits) identifies the category (e.g., 10 for Transport, 20 for Auth)
  • TTT (three digits) identifies the specific error within that category

This keeps diagnostics easy to scan while preserving enough room for future error types. Refer to the table below for the current registry.

Code Category Description
10001 Transport Transport failure
10002 Transport Unable to establish connection with the server
10003 Transport Malformed or unexpected server response
10004 Transport Authentication with the server failed
10005 Transport Network connectivity or policy failure
10006 Transport Invalid transport payload
10007 Transport Transport registration or selection error
20001 Auth Authentication subsystem error
20002 Auth Authentication configuration is invalid
20003 Auth Authentication provider is misconfigured
30001 Timeout Operation timed out
30002 Timeout Subprocess execution timed out
30003 Timeout Network request timed out
40001 Safety Safety policy violated
40002 Safety Network access blocked by safety policy
40003 Safety System command blocked by safety policy
40004 Safety Filesystem access blocked by safety policy
50001 Server Server returned an error
50002 Server Server is unavailable or not responding
50003 Server Protocol negotiation failed
60001 CLI CLI error
60002 CLI Invalid CLI arguments
70001 Reporting Reporting error
70002 Reporting Report validation failed
80001 Config Configuration error
80002 Config Configuration file could not be read
80003 Config Configuration validation failed
90001 Fuzzing Fuzzing engine error
90002 Fuzzing Fuzzing strategy failed
90003 Fuzzing Async executor encountered an error
95001 Runtime Runtime management error
95002 Runtime Failed to start managed process
95003 Runtime Failed to stop managed process
95004 Runtime Failed to send process signal
95005 Runtime Process registration failed
95006 Runtime Process watchdog failed to start

Each exception class in mcp_fuzzer/exceptions.py sets its code and description fields so CLI output, logs, and structured reports can reference these values. Use MCPError.to_metadata() or get_error_registry() to fetch the mapping programmatically.