fix: Add Types field to mcp-exec arguments parameter schema

The mcp-exec tool's 'arguments' parameter had the same issue as mcp-config-set -
missing type specification causing validation errors with Fireworks AI.

Added the Types field to specify that arguments can be any valid JSON type:
string, number, boolean, object, array, or null.

This resolves the 500 error:
"JSON Schema not supported: could not understand the instance
`{'description': 'Arguments to pass to the tool (can be any valid JSON value)'}`"

Tested with:
- Claude Code: mcp-exec works with object arguments
- Fireworks AI (via vai): 500 errors are resolved

Co-Authored-By: Aiden <[email protected]>

Author: jcheek

pkg/gateway/dynamic_mcps.go

@@ -939,6 +939,7 @@ func (g *Gateway) createMcpExecTool() *ToolRegistration {
 					Description: "Name of the tool to execute",
 				},
 				"arguments": {
+					Types:       []string{"string", "number", "boolean", "object", "array", "null"},
 					Description: "Arguments to pass to the tool (can be any valid JSON value)",
 				},
 			},