Add type checks

src/main.rs

@@ -14,7 +14,8 @@ use std::{
 };
 
 use dust_lib::{
-    eval, eval_with_context, gui::GuiApp, Result, Tool, ToolInfo, Value, VariableMap, TOOL_LIST,
+    eval, eval_with_context, tools::gui::GuiApp, Result, Tool, ToolInfo, Value, VariableMap,
+    TOOL_LIST,
 };
 
 /// Command-line arguments to be parsed.

src/tools/data_formats.rs

@@ -10,7 +10,7 @@ impl Tool for FromJson {
             identifier: "from_json",
             description: "Get a whale value from a JSON string.",
             group: "data",
-            inputs: vec![],
+            inputs: vec![ValueType::String],
         }
     }
 

src/tools/network.rs

@@ -1,6 +1,6 @@
 //! Macros for network access.
 
-use crate::{Result, Tool, ToolInfo, Value};
+use crate::{Result, Tool, ToolInfo, Value, ValueType};
 
 pub struct Download;
 
@@ -10,7 +10,7 @@ impl Tool for Download {
             identifier: "download",
             description: "Fetch a network resource.",
             group: "network",
-            inputs: vec![],
+            inputs: vec![ValueType::String],
         }
     }