chore(codersdk/toolsdk): improve static analyzability of toolsdk.Tools (#17562)

* Refactors toolsdk.Tools to remove opaque `map[string]any` argument in
favour of typed args structs.
* Refactors toolsdk.Tools to remove opaque passing of dependencies via
`context.Context` in favour of a tool dependencies struct.
* Adds panic recovery and clean context middleware to all tools.
* Adds `GenericTool` implementation to allow keeping `toolsdk.All` with
uniform type signature while maintaining type information in handlers.
* Adds stricter checks to `patchWorkspaceAgentAppStatus` handler.

cli/exp_mcp.go

@@ -1,6 +1,7 @@
 package cli
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"errors"
@@ -427,22 +428,27 @@ func mcpServerHandler(inv *serpent.Invocation, client *codersdk.Client, instruct
 		server.WithInstructions(instructions),
 	)
 
-	// Create a new context for the tools with all relevant information.
-	clientCtx := toolsdk.WithClient(ctx, client)
 	// Get the workspace agent token from the environment.
+	toolOpts := make([]func(*toolsdk.Deps), 0)
 	var hasAgentClient bool
 	if agentToken, err := getAgentToken(fs); err == nil && agentToken != "" {
 		hasAgentClient = true
 		agentClient := agentsdk.New(client.URL)
 		agentClient.SetSessionToken(agentToken)
-		clientCtx = toolsdk.WithAgentClient(clientCtx, agentClient)
+		toolOpts = append(toolOpts, toolsdk.WithAgentClient(agentClient))
 	} else {
 		cliui.Warnf(inv.Stderr, "CODER_AGENT_TOKEN is not set, task reporting will not be available")
 	}
-	if appStatusSlug == "" {
-		cliui.Warnf(inv.Stderr, "CODER_MCP_APP_STATUS_SLUG is not set, task reporting will not be available.")
+
+	if appStatusSlug != "" {
+		toolOpts = append(toolOpts, toolsdk.WithAppStatusSlug(appStatusSlug))
 	} else {
-		clientCtx = toolsdk.WithWorkspaceAppStatusSlug(clientCtx, appStatusSlug)
+		cliui.Warnf(inv.Stderr, "CODER_MCP_APP_STATUS_SLUG is not set, task reporting will not be available.")
+	}
+
+	toolDeps, err := toolsdk.NewDeps(client, toolOpts...)
+	if err != nil {
+		return xerrors.Errorf("failed to initialize tool dependencies: %w", err)
 	}
 
 	// Register tools based on the allowlist (if specified)
@@ -455,7 +461,7 @@ func mcpServerHandler(inv *serpent.Invocation, client *codersdk.Client, instruct
 		if len(allowedTools) == 0 || slices.ContainsFunc(allowedTools, func(t string) bool {
 			return t == tool.Tool.Name
 		}) {
-			mcpSrv.AddTools(mcpFromSDK(tool))
+			mcpSrv.AddTools(mcpFromSDK(tool, toolDeps))
 		}
 	}
 
@@ -463,7 +469,7 @@ func mcpServerHandler(inv *serpent.Invocation, client *codersdk.Client, instruct
 	done := make(chan error)
 	go func() {
 		defer close(done)
-		srvErr := srv.Listen(clientCtx, invStdin, invStdout)
+		srvErr := srv.Listen(ctx, invStdin, invStdout)
 		done <- srvErr
 	}()
 
@@ -726,7 +732,7 @@ func getAgentToken(fs afero.Fs) (string, error) {
 
 // mcpFromSDK adapts a toolsdk.Tool to go-mcp's server.ServerTool.
 // It assumes that the tool responds with a valid JSON object.
-func mcpFromSDK(sdkTool toolsdk.Tool[any]) server.ServerTool {
+func mcpFromSDK(sdkTool toolsdk.GenericTool, tb toolsdk.Deps) server.ServerTool {
 	// NOTE: some clients will silently refuse to use tools if there is an issue
 	// with the tool's schema or configuration.
 	if sdkTool.Schema.Properties == nil {
@@ -743,27 +749,17 @@ func mcpFromSDK(sdkTool toolsdk.Tool[any]) server.ServerTool {
 			},
 		},
 		Handler: func(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
-			result, err := sdkTool.Handler(ctx, request.Params.Arguments)
+			var buf bytes.Buffer
+			if err := json.NewEncoder(&buf).Encode(request.Params.Arguments); err != nil {
+				return nil, xerrors.Errorf("failed to encode request arguments: %w", err)
+			}
+			result, err := sdkTool.Handler(ctx, tb, buf.Bytes())
 			if err != nil {
 				return nil, err
 			}
-			var sb strings.Builder
-			if err := json.NewEncoder(&sb).Encode(result); err == nil {
-				return &mcp.CallToolResult{
-					Content: []mcp.Content{
-						mcp.NewTextContent(sb.String()),
-					},
-				}, nil
-			}
-			// If the result is not JSON, return it as a string.
-			// This is a fallback for tools that return non-JSON data.
-			resultStr, ok := result.(string)
-			if !ok {
-				return nil, xerrors.Errorf("tool call result is neither valid JSON or a string, got: %T", result)
-			}
 			return &mcp.CallToolResult{
 				Content: []mcp.Content{
-					mcp.NewTextContent(resultStr),
+					mcp.NewTextContent(string(result)),
 				},
 			}, nil
 		},

cli/exp_mcp_test.go

@@ -31,12 +31,12 @@ func TestExpMcpServer(t *testing.T) {
 		t.Parallel()
 
 		ctx := testutil.Context(t, testutil.WaitShort)
+		cmdDone := make(chan struct{})
 		cancelCtx, cancel := context.WithCancel(ctx)
-		t.Cleanup(cancel)
 
 		// Given: a running coder deployment
 		client := coderdtest.New(t, nil)
-		_ = coderdtest.CreateFirstUser(t, client)
+		owner := coderdtest.CreateFirstUser(t, client)
 
 		// Given: we run the exp mcp command with allowed tools set
 		inv, root := clitest.New(t, "exp", "mcp", "server", "--allowed-tools=coder_get_authenticated_user")
@@ -48,7 +48,6 @@ func TestExpMcpServer(t *testing.T) {
 		// nolint: gocritic // not the focus of this test
 		clitest.SetupConfig(t, client, root)
 
-		cmdDone := make(chan struct{})
 		go func() {
 			defer close(cmdDone)
 			err := inv.Run()
@@ -61,9 +60,6 @@ func TestExpMcpServer(t *testing.T) {
 		_ = pty.ReadLine(ctx) // ignore echoed output
 		output := pty.ReadLine(ctx)
 
-		cancel()
-		<-cmdDone
-
 		// Then: we should only see the allowed tools in the response
 		var toolsResponse struct {
 			Result struct {
@@ -81,6 +77,20 @@ func TestExpMcpServer(t *testing.T) {
 		}
 		slices.Sort(foundTools)
 		require.Equal(t, []string{"coder_get_authenticated_user"}, foundTools)
+
+		// Call the tool and ensure it works.
+		toolPayload := `{"jsonrpc":"2.0","id":3,"method":"tools/call", "params": {"name": "coder_get_authenticated_user", "arguments": {}}}`
+		pty.WriteLine(toolPayload)
+		_ = pty.ReadLine(ctx) // ignore echoed output
+		output = pty.ReadLine(ctx)
+		require.NotEmpty(t, output, "should have received a response from the tool")
+		// Ensure it's valid JSON
+		_, err = json.Marshal(output)
+		require.NoError(t, err, "should have received a valid JSON response from the tool")
+		// Ensure the tool returns the expected user
+		require.Contains(t, output, owner.UserID.String(), "should have received the expected user ID")
+		cancel()
+		<-cmdDone
 	})
 
 	t.Run("OK", func(t *testing.T) {