feat: add coder_workspace_write_file MCP tool (#19591)

codersdk/toolsdk/toolsdk.go

@@ -43,6 +43,7 @@ const (
 	ToolNameChatGPTSearch               = "search"
 	ToolNameChatGPTFetch                = "fetch"
 	ToolNameWorkspaceReadFile           = "coder_workspace_read_file"
+	ToolNameWorkspaceWriteFile          = "coder_workspace_write_file"
 )
 
 func NewDeps(client *codersdk.Client, opts ...func(*Deps)) (Deps, error) {
@@ -211,6 +212,7 @@ var All = []GenericTool{
 	ChatGPTSearch.Generic(),
 	ChatGPTFetch.Generic(),
 	WorkspaceReadFile.Generic(),
+	WorkspaceWriteFile.Generic(),
 }
 
 type ReportTaskArgs struct {
@@ -1441,6 +1443,54 @@ var WorkspaceReadFile = Tool[WorkspaceReadFileArgs, WorkspaceReadFileResponse]{
 	},
 }
 
+type WorkspaceWriteFileArgs struct {
+	Workspace string `json:"workspace"`
+	Path      string `json:"path"`
+	Content   []byte `json:"content"`
+}
+
+var WorkspaceWriteFile = Tool[WorkspaceWriteFileArgs, codersdk.Response]{
+	Tool: aisdk.Tool{
+		Name:        ToolNameWorkspaceWriteFile,
+		Description: `Write a file in a workspace.`,
+		Schema: aisdk.Schema{
+			Properties: map[string]any{
+				"workspace": map[string]any{
+					"type":        "string",
+					"description": "The workspace name in the format [owner/]workspace[.agent]. If an owner is not specified, the authenticated user is used.",
+				},
+				"path": map[string]any{
+					"type":        "string",
+					"description": "The absolute path of the file to write in the workspace.",
+				},
+				"content": map[string]any{
+					"type":        "string",
+					"description": "The base64-encoded bytes to write to the file.",
+				},
+			},
+			Required: []string{"path", "workspace", "content"},
+		},
+	},
+	UserClientOptional: true,
+	Handler: func(ctx context.Context, deps Deps, args WorkspaceWriteFileArgs) (codersdk.Response, error) {
+		conn, err := newAgentConn(ctx, deps.coderClient, args.Workspace)
+		if err != nil {
+			return codersdk.Response{}, err
+		}
+		defer conn.Close()
+
+		reader := bytes.NewReader(args.Content)
+		err = conn.WriteFile(ctx, args.Path, reader)
+		if err != nil {
+			return codersdk.Response{}, err
+		}
+
+		return codersdk.Response{
+			Message: "File written successfully.",
+		}, nil
+	},
+}
+
 // NormalizeWorkspaceInput converts workspace name input to standard format.
 // Handles the following input formats:
 //   - workspace                    → workspace

codersdk/toolsdk/toolsdk_test.go

@@ -555,6 +555,30 @@ func TestTools(t *testing.T) {
 			})
 		}
 	})
+
+	t.Run("WorkspaceWriteFile", func(t *testing.T) {
+		t.Parallel()
+
+		client, workspace, agentToken := setupWorkspaceForAgent(t)
+		fs := afero.NewMemMapFs()
+		_ = agenttest.New(t, client.URL, agentToken, func(opts *agent.Options) {
+			opts.Filesystem = fs
+		})
+		coderdtest.NewWorkspaceAgentWaiter(t, client, workspace.ID).Wait()
+		tb, err := toolsdk.NewDeps(client)
+		require.NoError(t, err)
+
+		_, err = testTool(t, toolsdk.WorkspaceWriteFile, tb, toolsdk.WorkspaceWriteFileArgs{
+			Workspace: workspace.Name,
+			Path:      "/test/some/path",
+			Content:   []byte("content"),
+		})
+		require.NoError(t, err)
+
+		b, err := afero.ReadFile(fs, "/test/some/path")
+		require.NoError(t, err)
+		require.Equal(t, []byte("content"), b)
+	})
 }
 
 // TestedTools keeps track of which tools have been tested.

codersdk/workspacesdk/agentconn.go

@@ -61,6 +61,7 @@ type AgentConn interface {
 	ReconnectingPTY(ctx context.Context, id uuid.UUID, height uint16, width uint16, command string, initOpts ...AgentReconnectingPTYInitOption) (net.Conn, error)
 	RecreateDevcontainer(ctx context.Context, devcontainerID string) (codersdk.Response, error)
 	ReadFile(ctx context.Context, path string, offset, limit int64) (io.ReadCloser, string, error)
+	WriteFile(ctx context.Context, path string, reader io.Reader) error
 	SSH(ctx context.Context) (*gonet.TCPConn, error)
 	SSHClient(ctx context.Context) (*ssh.Client, error)
 	SSHClientOnPort(ctx context.Context, port uint16) (*ssh.Client, error)
@@ -501,6 +502,27 @@ func (c *agentConn) ReadFile(ctx context.Context, path string, offset, limit int
 	return res.Body, mimeType, nil
 }
 
+// WriteFile writes to a file in the workspace.
+func (c *agentConn) WriteFile(ctx context.Context, path string, reader io.Reader) error {
+	ctx, span := tracing.StartSpan(ctx)
+	defer span.End()
+
+	res, err := c.apiRequest(ctx, http.MethodPost, fmt.Sprintf("/api/v0/write-file?path=%s", path), reader)
+	if err != nil {
+		return xerrors.Errorf("do request: %w", err)
+	}
+	defer res.Body.Close()
+	if res.StatusCode != http.StatusOK {
+		return codersdk.ReadBodyAsError(res)
+	}
+
+	var m codersdk.Response
+	if err := json.NewDecoder(res.Body).Decode(&m); err != nil {
+		return xerrors.Errorf("decode response body: %w", err)
+	}
+	return nil
+}
+
 // apiRequest makes a request to the workspace agent's HTTP API server.
 func (c *agentConn) apiRequest(ctx context.Context, method, path string, body io.Reader) (*http.Response, error) {
 	ctx, span := tracing.StartSpan(ctx)

codersdk/workspacesdk/agentconnmock/agentconnmock.go

@@ -387,3 +387,17 @@ func (mr *MockAgentConnMockRecorder) WatchContainers(ctx, logger any) *gomock.Ca
 	mr.mock.ctrl.T.Helper()
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "WatchContainers", reflect.TypeOf((*MockAgentConn)(nil).WatchContainers), ctx, logger)
 }
+
+// WriteFile mocks base method.
+func (m *MockAgentConn) WriteFile(ctx context.Context, path string, reader io.Reader) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "WriteFile", ctx, path, reader)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// WriteFile indicates an expected call of WriteFile.
+func (mr *MockAgentConnMockRecorder) WriteFile(ctx, path, reader any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "WriteFile", reflect.TypeOf((*MockAgentConn)(nil).WriteFile), ctx, path, reader)
+}