feat[Go]: implement GET /plugin/tools (issue #15240) (#15570)

## Summary

Port the Python `GET /v1/plugin/tools` endpoint to the Go API server.
Listed in the Go-API port checklist of #15240.

Returns the metadata of every embedded LLM tool plugin in the same JSON
shape the Python endpoint emits (camelCase keys preserved), so existing
frontends bind to the Go server without changes.

cmd/server_main.go

@@ -219,6 +219,7 @@ func startServer(config *server.Config) {
 		tenantService,
 		&handler.SearchbotRealLLM{Svc: modelProviderService},
 	)
+	pluginHandler := handler.NewPluginHandler(service.NewPluginService())
 
 	// Dify retrieval handler
 	docDAO := dao.NewDocumentDAO()
@@ -233,7 +234,7 @@ func startServer(config *server.Config) {
 	)
 
 	// Initialize router
-	r := router.NewRouter(authHandler, userHandler, tenantHandler, documentHandler, datasetsHandler, systemHandler, knowledgebaseHandler, chunkHandler, llmHandler, chatHandler, chatSessionHandler, connectorHandler, searchHandler, fileHandler, memoryHandler, mcpHandler, skillSearchHandler, providerHandler, agentHandler, relatedQuestionsHandler, difyRetrievalHandler)
+	r := router.NewRouter(authHandler, userHandler, tenantHandler, documentHandler, datasetsHandler, systemHandler, knowledgebaseHandler, chunkHandler, llmHandler, chatHandler, chatSessionHandler, connectorHandler, searchHandler, fileHandler, memoryHandler, mcpHandler, skillSearchHandler, providerHandler, agentHandler, relatedQuestionsHandler, difyRetrievalHandler, pluginHandler)
 
 	// Create Gin engine
 	ginEngine := gin.New()

internal/handler/plugin.go

@@ -0,0 +1,61 @@
+//
+//  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+//
+
+package handler
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+
+	"ragflow/internal/common"
+	"ragflow/internal/service"
+)
+
+// PluginHandler serves the /plugin/* HTTP routes.
+type PluginHandler struct {
+	pluginService *service.PluginService
+}
+
+// NewPluginHandler creates a plugin handler.
+func NewPluginHandler(pluginService *service.PluginService) *PluginHandler {
+	return &PluginHandler{
+		pluginService: pluginService,
+	}
+}
+
+// ListLLMTools handles GET /v1/plugin/tools.
+//
+// @Summary  List LLM tool plugins
+// @Description  Return the metadata of every embedded LLM tool plugin. Matches
+// @Description  the response of the Python GET /v1/plugin/tools endpoint.
+// @Tags     plugin
+// @Produce  json
+// @Security ApiKeyAuth
+// @Success  200 {object} map[string]interface{}
+// @Router   /v1/plugin/tools [get]
+func (h *PluginHandler) ListLLMTools(c *gin.Context) {
+	if _, errorCode, errorMessage := GetUser(c); errorCode != common.CodeSuccess {
+		jsonError(c, errorCode, errorMessage)
+		return
+	}
+
+	c.JSON(http.StatusOK, gin.H{
+		"code":    common.CodeSuccess,
+		"message": "success",
+		"data":    h.pluginService.ListLLMTools(),
+	})
+}

internal/handler/plugin_test.go

@@ -0,0 +1,173 @@
+//
+//  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+//
+
+package handler
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+
+	"ragflow/internal/common"
+	"ragflow/internal/entity"
+	"ragflow/internal/service"
+)
+
+func newPluginRouter(authenticate bool) (*gin.Engine, *PluginHandler) {
+	gin.SetMode(gin.TestMode)
+	h := NewPluginHandler(service.NewPluginService())
+	r := gin.New()
+	r.GET("/api/v1/plugin/tools", func(c *gin.Context) {
+		if authenticate {
+			c.Set("user", &entity.User{ID: "tenant-1"})
+		}
+		h.ListLLMTools(c)
+	})
+	return r, h
+}
+
+func TestPluginHandlerListLLMToolsReturnsEmbeddedMetadata(t *testing.T) {
+	r, _ := newPluginRouter(true)
+
+	resp := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/plugin/tools", nil)
+	r.ServeHTTP(resp, req)
+
+	if resp.Code != http.StatusOK {
+		t.Fatalf("status=%d body=%s", resp.Code, resp.Body.String())
+	}
+
+	var body struct {
+		Code    int                       `json:"code"`
+		Message string                    `json:"message"`
+		Data    []service.LLMToolMetadata `json:"data"`
+	}
+	if err := json.Unmarshal(resp.Body.Bytes(), &body); err != nil {
+		t.Fatalf("unmarshal response: %v body=%s", err, resp.Body.String())
+	}
+	if body.Code != int(common.CodeSuccess) {
+		t.Fatalf("code=%d want=%d body=%s", body.Code, common.CodeSuccess, resp.Body.String())
+	}
+	if body.Message != "success" {
+		t.Errorf("message=%q want=%q", body.Message, "success")
+	}
+	if len(body.Data) == 0 {
+		t.Fatalf("data should contain at least one embedded plugin, got 0")
+	}
+
+	// Verify bad_calculator is present with the exact metadata shape the Python
+	// endpoint returns, so existing clients can swap backends transparently.
+	var bad *service.LLMToolMetadata
+	for i := range body.Data {
+		if body.Data[i].Name == "bad_calculator" {
+			bad = &body.Data[i]
+			break
+		}
+	}
+	if bad == nil {
+		t.Fatalf("bad_calculator missing from data=%+v", body.Data)
+	}
+	if bad.DisplayName != "$t:bad_calculator.name" {
+		t.Errorf("displayName=%q want %q", bad.DisplayName, "$t:bad_calculator.name")
+	}
+	if bad.Description == "" {
+		t.Errorf("description must be non-empty")
+	}
+	for _, k := range []string{"a", "b"} {
+		p, ok := bad.Parameters[k]
+		if !ok {
+			t.Errorf("parameter %q missing", k)
+			continue
+		}
+		if p.Type != "number" {
+			t.Errorf("param %q type=%q want number", k, p.Type)
+		}
+		if !p.Required {
+			t.Errorf("param %q must be required", k)
+		}
+	}
+}
+
+func TestPluginHandlerListLLMToolsResponseFieldNamesMatchPython(t *testing.T) {
+	// Defensive check: the raw JSON keys (not Go field names) must match the
+	// camelCase keys the Python endpoint emits. Snake_case here would break
+	// any frontend that already binds to the Python contract.
+	r, _ := newPluginRouter(true)
+
+	resp := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/plugin/tools", nil)
+	r.ServeHTTP(resp, req)
+
+	var envelope struct {
+		Data []map[string]interface{} `json:"data"`
+	}
+	if err := json.Unmarshal(resp.Body.Bytes(), &envelope); err != nil {
+		t.Fatalf("unmarshal: %v", err)
+	}
+	if len(envelope.Data) == 0 {
+		t.Fatalf("data empty")
+	}
+	tool := envelope.Data[0]
+	for _, key := range []string{"name", "displayName", "description", "displayDescription", "parameters"} {
+		if _, ok := tool[key]; !ok {
+			t.Errorf("missing key %q in tool metadata, got keys=%v", key, mapKeys(tool))
+		}
+	}
+	params, ok := tool["parameters"].(map[string]interface{})
+	if !ok || len(params) == 0 {
+		t.Fatalf("parameters is not a non-empty object: %v", tool["parameters"])
+	}
+	for paramName, raw := range params {
+		paramObj, ok := raw.(map[string]interface{})
+		if !ok {
+			t.Fatalf("parameter %q is not an object", paramName)
+		}
+		for _, key := range []string{"type", "description", "displayDescription", "required"} {
+			if _, ok := paramObj[key]; !ok {
+				t.Errorf("parameter %q missing key %q (keys=%v)", paramName, key, mapKeys(paramObj))
+			}
+		}
+	}
+}
+
+func TestPluginHandlerListLLMToolsRejectsUnauthenticated(t *testing.T) {
+	r, _ := newPluginRouter(false)
+
+	resp := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodGet, "/api/v1/plugin/tools", nil)
+	r.ServeHTTP(resp, req)
+
+	// jsonError encodes the error code into the JSON body; HTTP status is
+	// still 200 in this codebase's response style, so check the body code.
+	var body map[string]interface{}
+	if err := json.Unmarshal(resp.Body.Bytes(), &body); err != nil {
+		t.Fatalf("unmarshal: %v body=%s", err, resp.Body.String())
+	}
+	if code, _ := body["code"].(float64); int(code) == int(common.CodeSuccess) {
+		t.Errorf("expected non-success code for unauthenticated request, got body=%v", body)
+	}
+}
+
+func mapKeys(m map[string]interface{}) []string {
+	out := make([]string, 0, len(m))
+	for k := range m {
+		out = append(out, k)
+	}
+	return out
+}

internal/router/router.go

@@ -43,7 +43,8 @@ type Router struct {
 	providerHandler         *handler.ProviderHandler
 	agentHandler            *handler.AgentHandler
 	relatedQuestionsHandler *handler.SearchbotHandler
-	difyRetrievalHandler  *handler.DifyRetrievalHandler
+	difyRetrievalHandler    *handler.DifyRetrievalHandler
+	pluginHandler           *handler.PluginHandler
 }
 
 // NewRouter create router
@@ -68,7 +69,8 @@ func NewRouter(
 	providerHandler *handler.ProviderHandler,
 	agentHandler *handler.AgentHandler,
 	relatedQuestionsHandler *handler.SearchbotHandler,
-	difyRetrievalHandler  *handler.DifyRetrievalHandler,
+	difyRetrievalHandler *handler.DifyRetrievalHandler,
+	pluginHandler *handler.PluginHandler,
 ) *Router {
 	return &Router{
 		authHandler:             authHandler,
@@ -91,7 +93,8 @@ func NewRouter(
 		providerHandler:         providerHandler,
 		agentHandler:            agentHandler,
 		relatedQuestionsHandler: relatedQuestionsHandler,
-			difyRetrievalHandler:  difyRetrievalHandler,
+		difyRetrievalHandler:    difyRetrievalHandler,
+		pluginHandler:           pluginHandler,
 	}
 }
 
@@ -379,6 +382,12 @@ func (r *Router) Setup(engine *gin.Engine) {
 				agents.PUT("/:agent_id/tags", r.agentHandler.UpdateAgentTags)
 			}
 
+			// Plugin routes
+			plugin := v1.Group("/plugin")
+			{
+				plugin.GET("/tools", r.pluginHandler.ListLLMTools)
+			}
+
 			connector := v1.Group("/connectors")
 			{
 				connector.GET("/", r.connectorHandler.ListConnectors)

internal/service/plugin.go

@@ -0,0 +1,89 @@
+//
+//  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+//
+
+package service
+
+// PluginService exposes metadata for embedded LLM tool plugins.
+//
+// The Python service discovers plugins dynamically from
+// agent/plugin/embedded_plugins/llm_tools via pluginlib. The Go server has no
+// runtime Python loader, so the embedded set is mirrored as a static table.
+// To add a plugin here, append to embeddedLLMTools below.
+type PluginService struct{}
+
+// NewPluginService creates a new plugin service.
+func NewPluginService() *PluginService {
+	return &PluginService{}
+}
+
+// LLMToolParameter mirrors agent.plugin.llm_tool_plugin.LLMToolParameter.
+type LLMToolParameter struct {
+	Type               string `json:"type"`
+	Description        string `json:"description"`
+	DisplayDescription string `json:"displayDescription"`
+	Required           bool   `json:"required"`
+}
+
+// LLMToolMetadata mirrors agent.plugin.llm_tool_plugin.LLMToolMetadata.
+type LLMToolMetadata struct {
+	Name               string                      `json:"name"`
+	DisplayName        string                      `json:"displayName"`
+	Description        string                      `json:"description"`
+	DisplayDescription string                      `json:"displayDescription"`
+	Parameters         map[string]LLMToolParameter `json:"parameters"`
+}
+
+var embeddedLLMTools = []LLMToolMetadata{
+	{
+		Name:               "bad_calculator",
+		DisplayName:        "$t:bad_calculator.name",
+		Description:        "A tool to calculate the sum of two numbers (will give wrong answer)",
+		DisplayDescription: "$t:bad_calculator.description",
+		Parameters: map[string]LLMToolParameter{
+			"a": {
+				Type:               "number",
+				Description:        "The first number",
+				DisplayDescription: "$t:bad_calculator.params.a",
+				Required:           true,
+			},
+			"b": {
+				Type:               "number",
+				Description:        "The second number",
+				DisplayDescription: "$t:bad_calculator.params.b",
+				Required:           true,
+			},
+		},
+	},
+}
+
+// ListLLMTools returns the metadata of every embedded LLM tool plugin in the
+// same order, shape and field names as the Python /plugin/tools endpoint.
+//
+// The returned slice and its nested Parameters maps are fresh copies — callers
+// may mutate the result without affecting other requests or the package-level
+// embeddedLLMTools table.
+func (s *PluginService) ListLLMTools() []LLMToolMetadata {
+	out := make([]LLMToolMetadata, len(embeddedLLMTools))
+	copy(out, embeddedLLMTools)
+	for i := range out {
+		params := make(map[string]LLMToolParameter, len(out[i].Parameters))
+		for k, v := range out[i].Parameters {
+			params[k] = v
+		}
+		out[i].Parameters = params
+	}
+	return out
+}