Validate tool params and add tests

nanobot/agent/tools/base.py

@@ -43,6 +43,79 @@ class Tool(ABC):
         """
         pass
 
+    def validate_params(self, params: dict[str, Any]) -> list[str]:
+        """
+        Lightweight JSON schema validation for tool parameters.
+
+        Returns a list of error strings (empty if valid).
+        Unknown params are ignored.
+        """
+        schema = self.parameters or {}
+        if schema.get("type") != "object":
+            return []
+
+        return self._validate_schema(params, schema, path="")
+
+    def _validate_schema(self, value: Any, schema: dict[str, Any], path: str) -> list[str]:
+        errors: list[str] = []
+        expected_type = schema.get("type")
+
+        type_map = {
+            "string": str,
+            "integer": int,
+            "number": (int, float),
+            "boolean": bool,
+            "array": list,
+            "object": dict,
+        }
+
+        def label(p: str) -> str:
+            return p or "parameter"
+
+        if expected_type in type_map and not isinstance(value, type_map[expected_type]):
+            errors.append(f"{label(path)} should be {expected_type}")
+            return errors
+
+        if "enum" in schema and value not in schema["enum"]:
+            errors.append(f"{label(path)} must be one of {schema['enum']}")
+
+        if expected_type in ("integer", "number"):
+            if "minimum" in schema and value < schema["minimum"]:
+                errors.append(f"{label(path)} must be >= {schema['minimum']}")
+            if "maximum" in schema and value > schema["maximum"]:
+                errors.append(f"{label(path)} must be <= {schema['maximum']}")
+
+        if expected_type == "string":
+            if "minLength" in schema and len(value) < schema["minLength"]:
+                errors.append(f"{label(path)} must be at least {schema['minLength']} chars")
+            if "maxLength" in schema and len(value) > schema["maxLength"]:
+                errors.append(f"{label(path)} must be at most {schema['maxLength']} chars")
+
+        if expected_type == "object":
+            properties = schema.get("properties", {}) or {}
+            required = set(schema.get("required", []) or [])
+
+            for key in required:
+                if key not in value:
+                    p = f"{path}.{key}" if path else key
+                    errors.append(f"missing required {p}")
+
+            for key, item in value.items():
+                prop_schema = properties.get(key)
+                if not prop_schema:
+                    continue  # ignore unknown fields
+                p = f"{path}.{key}" if path else key
+                errors.extend(self._validate_schema(item, prop_schema, p))
+
+        if expected_type == "array":
+            items_schema = schema.get("items")
+            if items_schema:
+                for idx, item in enumerate(value):
+                    p = f"{path}[{idx}]" if path else f"[{idx}]"
+                    errors.extend(self._validate_schema(item, items_schema, p))
+
+        return errors
+    
     def to_schema(self) -> dict[str, Any]:
         """Convert tool to OpenAI function schema format."""
         return {

nanobot/agent/tools/registry.py

@@ -54,6 +54,9 @@ class ToolRegistry:
             return f"Error: Tool '{name}' not found"
 
         try:
+            errors = tool.validate_params(params)
+            if errors:
+                return f"Error: Invalid parameters for tool '{name}': " + "; ".join(errors)
             return await tool.execute(**params)
         except Exception as e:
             return f"Error executing {name}: {str(e)}"

tests/test_tool_validation.py

@@ -0,0 +1,88 @@
+from typing import Any
+
+from nanobot.agent.tools.base import Tool
+from nanobot.agent.tools.registry import ToolRegistry
+
+
+class SampleTool(Tool):
+    @property
+    def name(self) -> str:
+        return "sample"
+
+    @property
+    def description(self) -> str:
+        return "sample tool"
+
+    @property
+    def parameters(self) -> dict[str, Any]:
+        return {
+            "type": "object",
+            "properties": {
+                "query": {"type": "string", "minLength": 2},
+                "count": {"type": "integer", "minimum": 1, "maximum": 10},
+                "mode": {"type": "string", "enum": ["fast", "full"]},
+                "meta": {
+                    "type": "object",
+                    "properties": {
+                        "tag": {"type": "string"},
+                        "flags": {
+                            "type": "array",
+                            "items": {"type": "string"},
+                        },
+                    },
+                    "required": ["tag"],
+                },
+            },
+            "required": ["query", "count"],
+        }
+
+    async def execute(self, **kwargs: Any) -> str:
+        return "ok"
+
+
+def test_validate_params_missing_required() -> None:
+    tool = SampleTool()
+    errors = tool.validate_params({"query": "hi"})
+    assert "missing required count" in "; ".join(errors)
+
+
+def test_validate_params_type_and_range() -> None:
+    tool = SampleTool()
+    errors = tool.validate_params({"query": "hi", "count": 0})
+    assert any("count must be >= 1" in e for e in errors)
+
+    errors = tool.validate_params({"query": "hi", "count": "2"})
+    assert any("count should be integer" in e for e in errors)
+
+
+def test_validate_params_enum_and_min_length() -> None:
+    tool = SampleTool()
+    errors = tool.validate_params({"query": "h", "count": 2, "mode": "slow"})
+    assert any("query must be at least 2 chars" in e for e in errors)
+    assert any("mode must be one of" in e for e in errors)
+
+
+def test_validate_params_nested_object_and_array() -> None:
+    tool = SampleTool()
+    errors = tool.validate_params(
+        {
+            "query": "hi",
+            "count": 2,
+            "meta": {"flags": [1, "ok"]},
+        }
+    )
+    assert any("missing required meta.tag" in e for e in errors)
+    assert any("meta.flags[0] should be string" in e for e in errors)
+
+
+def test_validate_params_ignores_unknown_fields() -> None:
+    tool = SampleTool()
+    errors = tool.validate_params({"query": "hi", "count": 2, "extra": "x"})
+    assert errors == []
+
+
+async def test_registry_returns_validation_error() -> None:
+    reg = ToolRegistry()
+    reg.register(SampleTool())
+    result = await reg.execute("sample", {"query": "hi"})
+    assert "Invalid parameters" in result