feat: add ClientMetadata to ToolResultPart

agent.go

@@ -642,6 +642,7 @@ func toResponseMessages(content []Content) []Message {
 				Output:           result.Result,
 				ProviderExecuted: result.ProviderExecuted,
 				ProviderOptions:  ProviderOptions(result.ProviderMetadata),
+				ClientMetadata:   result.ClientMetadata,
 			}
 			if result.ProviderExecuted {
 				// Provider-executed tool results (e.g. web search)

agent_test.go

@@ -1918,8 +1918,9 @@ func TestToResponseMessages_ProviderExecutedRouting(t *testing.T) {
 		},
 		// Regular tool result.
 		&ToolResultContent{
-			ToolCallID: "toolu_02",
-			Result:     ToolResultOutputContentText{Text: "2"},
+			ToolCallID:     "toolu_02",
+			Result:         ToolResultOutputContentText{Text: "2"},
+			ClientMetadata: `{"precision":"high"}`,
 		},
 		// Some trailing text.
 		&TextContent{Text: "Done."},
@@ -1967,9 +1968,11 @@ func TestToResponseMessages_ProviderExecutedRouting(t *testing.T) {
 	require.Equal(t, MessageRoleTool, toolMsg.Role)
 	require.Len(t, toolMsg.Content, 1)
 
+	// Verify regular tool result is in tool message and client metadata survived.
 	tr2, ok := AsMessagePart[ToolResultPart](toolMsg.Content[0])
 	require.True(t, ok)
 	require.Equal(t, "toolu_02", tr2.ToolCallID)
+	require.Equal(t, `{"precision":"high"}`, tr2.ClientMetadata)
 	require.False(t, tr2.ProviderExecuted)
 }
 

content.go

@@ -259,6 +259,7 @@ type ToolResultPart struct {
 	Output           ToolResultOutputContent `json:"output"`
 	ProviderExecuted bool                    `json:"provider_executed"`
 	ProviderOptions  ProviderOptions         `json:"provider_options"`
+	ClientMetadata   string                  `json:"client_metadata,omitempty"`
 }
 
 // GetType returns the type of the tool result part.

content_json.go

@@ -715,11 +715,13 @@ func (t ToolResultPart) MarshalJSON() ([]byte, error) {
 		Output           ToolResultOutputContent `json:"output"`
 		ProviderExecuted bool                    `json:"provider_executed"`
 		ProviderOptions  ProviderOptions         `json:"provider_options,omitempty"`
+		ClientMetadata   string                  `json:"client_metadata,omitempty"`
 	}{
 		ToolCallID:       t.ToolCallID,
 		Output:           t.Output,
 		ProviderExecuted: t.ProviderExecuted,
 		ProviderOptions:  t.ProviderOptions,
+		ClientMetadata:   t.ClientMetadata,
 	})
 	if err != nil {
 		return nil, err
@@ -743,6 +745,7 @@ func (t *ToolResultPart) UnmarshalJSON(data []byte) error {
 		Output           json.RawMessage            `json:"output"`
 		ProviderExecuted bool                       `json:"provider_executed"`
 		ProviderOptions  map[string]json.RawMessage `json:"provider_options,omitempty"`
+		ClientMetadata   string                     `json:"client_metadata,omitempty"`
 	}
 
 	if err := json.Unmarshal(mpj.Data, &aux); err != nil {
@@ -751,6 +754,7 @@ func (t *ToolResultPart) UnmarshalJSON(data []byte) error {
 
 	t.ToolCallID = aux.ToolCallID
 	t.ProviderExecuted = aux.ProviderExecuted
+	t.ClientMetadata = aux.ClientMetadata
 
 	// Unmarshal the Output field
 	output, err := UnmarshalToolResultOutputContent(aux.Output)

json_test.go

@@ -80,6 +80,7 @@ func TestMessageJSONSerialization(t *testing.T) {
 						Output: ToolResultOutputContentText{
 							Text: "The weather is sunny, 72°F",
 						},
+						ClientMetadata: `{"units":"imperial"}`,
 					},
 				},
 			},
@@ -245,6 +246,9 @@ func compareMessagePart(t *testing.T, index int, original, decoded MessagePart)
 		if orig.ToolCallID != dec.ToolCallID {
 			t.Errorf("content[%d] tool result call id mismatch: got %q, want %q", index, dec.ToolCallID, orig.ToolCallID)
 		}
+		if orig.ClientMetadata != dec.ClientMetadata {
+			t.Errorf("content[%d] tool result client metadata mismatch: got %q, want %q", index, dec.ClientMetadata, orig.ClientMetadata)
+		}
 		compareToolResultOutput(t, index, orig.Output, dec.Output)
 	}
 }