Function TestMCPServerToolInvocation

coderd/x/chatd/chatd_test.go:7663–7845

TestMCPServerToolInvocation verifies that when a chat has mcp_server_ids set, the chat loop connects to those MCP servers, discovers their tools, and the LLM can invoke them. NOTE: This test uses a raw database.Store (no dbauthz wrapper). The chatd RBAC authorization of GetMCPServerConfigsByIDs (wh

(t *testing.T)

// requires ActionRead on ResourceDeploymentConfig) is covered by
// the chatd role definition tests, not here.
func TestMCPServerToolInvocation(t *testing.T) {
	t.Parallel()

	db, ps := dbtestutil.NewDB(t)
	ctx := testutil.Context(t, testutil.WaitLong)

	// Start a real MCP server that exposes an "echo" tool.
	mcpSrv := mcpserver.NewMCPServer("test-mcp", "1.0.0")
	mcpSrv.AddTools(mcpserver.ServerTool{
		Tool: mcpgo.NewTool("echo",
			mcpgo.WithDescription("Echoes the input"),
			mcpgo.WithString("input",
				mcpgo.Description("The input string"),
				mcpgo.Required(),
			),
		),
		Handler: func(_ context.Context, req mcpgo.CallToolRequest) (*mcpgo.CallToolResult, error) {
			input, _ := req.GetArguments()["input"].(string)
			return mcpgo.NewToolResultText("echo: " + input), nil
		},
	})
	mcpHTTP := mcpserver.NewStreamableHTTPServer(mcpSrv)
	mcpTS := httptest.NewServer(mcpHTTP)
	t.Cleanup(mcpTS.Close)

	// Track which tool names are sent to the LLM and capture
	// whether the MCP tool result appears in the second call.
	var (
		callCount      atomic.Int32
		llmToolNames   []string
		llmToolsMu     sync.Mutex
		foundMCPResult atomic.Bool
	)

	openAIURL := chattest.NewOpenAI(t, func(req *chattest.OpenAIRequest) chattest.OpenAIResponse {
		if !req.Stream {
			return chattest.OpenAINonStreamingResponse("title")
		}

		// Record tool names from the first streamed call.
		if callCount.Add(1) == 1 {
			names := make([]string, 0, len(req.Tools))
			for _, tool := range req.Tools {
				names = append(names, tool.Function.Name)
			}
			llmToolsMu.Lock()
			llmToolNames = names
			llmToolsMu.Unlock()

			// Ask the LLM to call the MCP echo tool.
			return chattest.OpenAIStreamingResponse(
				chattest.OpenAIToolCallChunk(
					"test-mcp__echo",
					`{"input":"hello from LLM"}`,
				),
			)
		}