Implement Tag API methods (CRITICAL)

Add direct client methods for tag operations:

Must-have methods:
- GetTaskTags(ctx, taskID) - returns map[tagID]tagName
- SetTaskTags(ctx, projectID, taskID, tags) - replaces all tags

Nice-to-have methods:
- GetAllTags(ctx) - list all tags in system
- GetTagsByProject(ctx, projectID) - list project tags
- CreateTag(ctx, projectID, name, colorID) - create new tag
- UpdateTag(ctx, tagID, name, colorID) - update existing tag
- RemoveTag(ctx, tagID) - delete tag

Note: setTaskTags REPLACES all tags. Individual add/remove
requires read-modify-write pattern (to be implemented in TaskScope).

Closes: kanboard-api-16r

.beads/issues.jsonl

@@ -1,5 +1,5 @@
 {"id":"kanboard-api-0fz","title":"Implement Category API methods","description":"Implement direct API methods for category operations.\n\n## Methods to implement\n- GetAllCategories(ctx, projectID int) ([]Category, error) - getAllCategories\n- GetCategory(ctx, categoryID int) (*Category, error) - getCategory (Nice-to-have)\n\n## Files to create\n- categories.go\n\n## Acceptance criteria\n- Proper error handling\n- Returns empty slice when no categories exist","status":"open","priority":1,"issue_type":"feature","owner":"mail@oliverjakoubek.de","created_at":"2026-01-15T17:35:16.6133153+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-15T17:35:16.6133153+01:00","dependencies":[{"issue_id":"kanboard-api-0fz","depends_on_id":"kanboard-api-uls","type":"blocks","created_at":"2026-01-15T17:42:53.161416595+01:00","created_by":"Oliver Jakoubek"},{"issue_id":"kanboard-api-0fz","depends_on_id":"kanboard-api-cyc","type":"blocks","created_at":"2026-01-15T17:42:53.226963473+01:00","created_by":"Oliver Jakoubek"}]}
-{"id":"kanboard-api-16r","title":"Implement Tag API methods (CRITICAL)","description":"Implement direct API methods for tag operations. Tags are CRITICAL - heavily used.\n\n## Direct Client methods (Must-have)\n- GetTaskTags(ctx, taskID int) (map[int]string, error) - getTaskTags\n- SetTaskTags(ctx, projectID, taskID int, tags []string) error - setTaskTags\n\n## Direct Client methods (Nice-to-have)\n- GetAllTags(ctx) ([]Tag, error) - getAllTags\n- GetTagsByProject(ctx, projectID int) ([]Tag, error) - getTagsByProject\n- CreateTag(ctx, projectID int, name, colorID string) (int, error) - createTag\n- UpdateTag(ctx, tagID int, name, colorID string) error - updateTag\n- RemoveTag(ctx, tagID int) error - removeTag\n\n## Files to create\n- tags.go\n\n## IMPORTANT NOTE\nsetTaskTags REPLACES ALL tags. Individual add/remove requires read-modify-write pattern (implemented in TaskScope).\n\n## Acceptance criteria\n- GetTaskTags returns map[tagID]tagName\n- SetTaskTags accepts tag names (auto-creates if needed)","status":"open","priority":0,"issue_type":"feature","owner":"mail@oliverjakoubek.de","created_at":"2026-01-15T17:36:08.526810135+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-15T17:36:08.526810135+01:00","dependencies":[{"issue_id":"kanboard-api-16r","depends_on_id":"kanboard-api-uls","type":"blocks","created_at":"2026-01-15T17:43:49.223137796+01:00","created_by":"Oliver Jakoubek"},{"issue_id":"kanboard-api-16r","depends_on_id":"kanboard-api-cyc","type":"blocks","created_at":"2026-01-15T17:43:49.402237867+01:00","created_by":"Oliver Jakoubek"}]}
+{"id":"kanboard-api-16r","title":"Implement Tag API methods (CRITICAL)","description":"Implement direct API methods for tag operations. Tags are CRITICAL - heavily used.\n\n## Direct Client methods (Must-have)\n- GetTaskTags(ctx, taskID int) (map[int]string, error) - getTaskTags\n- SetTaskTags(ctx, projectID, taskID int, tags []string) error - setTaskTags\n\n## Direct Client methods (Nice-to-have)\n- GetAllTags(ctx) ([]Tag, error) - getAllTags\n- GetTagsByProject(ctx, projectID int) ([]Tag, error) - getTagsByProject\n- CreateTag(ctx, projectID int, name, colorID string) (int, error) - createTag\n- UpdateTag(ctx, tagID int, name, colorID string) error - updateTag\n- RemoveTag(ctx, tagID int) error - removeTag\n\n## Files to create\n- tags.go\n\n## IMPORTANT NOTE\nsetTaskTags REPLACES ALL tags. Individual add/remove requires read-modify-write pattern (implemented in TaskScope).\n\n## Acceptance criteria\n- GetTaskTags returns map[tagID]tagName\n- SetTaskTags accepts tag names (auto-creates if needed)","status":"closed","priority":0,"issue_type":"feature","owner":"mail@oliverjakoubek.de","created_at":"2026-01-15T17:36:08.526810135+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-15T18:20:17.392248254+01:00","closed_at":"2026-01-15T18:20:17.392248254+01:00","close_reason":"Closed","dependencies":[{"issue_id":"kanboard-api-16r","depends_on_id":"kanboard-api-uls","type":"blocks","created_at":"2026-01-15T17:43:49.223137796+01:00","created_by":"Oliver Jakoubek"},{"issue_id":"kanboard-api-16r","depends_on_id":"kanboard-api-cyc","type":"blocks","created_at":"2026-01-15T17:43:49.402237867+01:00","created_by":"Oliver Jakoubek"}]}
 {"id":"kanboard-api-25y","title":"Implement Timestamp type with JSON handling","description":"Implement custom Timestamp type that handles Kanboard's Unix timestamp format.\n\n## Requirements\n- Timestamp struct wrapping time.Time\n- UnmarshalJSON supporting:\n  - Unix timestamps as integers\n  - Empty strings and \"0\" as zero time\n  - Zero value (0) as zero time\n- MarshalJSON returning Unix timestamp or 0 for zero time\n\n## Files to create\n- timestamp.go\n\n## Acceptance criteria\n- Correctly parses integer Unix timestamps\n- Handles empty strings and \"0\" strings\n- Zero time marshals to 0\n- Non-zero time marshals to Unix timestamp","status":"closed","priority":0,"issue_type":"feature","owner":"mail@oliverjakoubek.de","created_at":"2026-01-15T17:34:55.0044989+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-15T18:15:27.299644047+01:00","closed_at":"2026-01-15T18:15:27.299644047+01:00","close_reason":"Closed"}
 {"id":"kanboard-api-2g1","title":"Implement JSON-RPC client foundation","description":"Implement the core JSON-RPC 2.0 client for Kanboard API communication.\n\n## Requirements\n- JSONRPCRequest struct with jsonrpc, method, id, params fields\n- JSONRPCResponse struct with jsonrpc, id, result, error fields  \n- JSONRPCError struct with code and message\n- Generic `call` method to send requests and parse responses\n- Automatic `/jsonrpc.php` path appending to baseURL\n- Thread-safe request ID generation via atomic.Int64\n\n## Files to create\n- jsonrpc.go\n\n## Acceptance criteria\n- All JSON-RPC structs properly marshal/unmarshal\n- Request IDs increment atomically\n- Supports subdirectory installations (e.g. /kanboard/jsonrpc.php)","status":"closed","priority":0,"issue_type":"feature","owner":"mail@oliverjakoubek.de","created_at":"2026-01-15T17:34:53.232007312+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-15T18:10:29.68466887+01:00","closed_at":"2026-01-15T18:10:29.68466887+01:00","close_reason":"Closed"}
 {"id":"kanboard-api-2ze","title":"Implement BoardScope fluent builder","description":"Implement BoardScope for fluent project-scoped operations.\n\n## Requirements\n- BoardScope struct with client and projectID\n- Client.Board(projectID int) *BoardScope method\n- BoardScope methods:\n  - GetColumns(ctx) ([]Column, error)\n  - GetCategories(ctx) ([]Category, error)\n  - GetTasks(ctx, status TaskStatus) ([]Task, error)\n  - SearchTasks(ctx, query string) ([]Task, error)\n  - CreateTask(ctx, task *TaskParams) (*Task, error)\n\n## Files to create\n- board_scope.go\n\n## Example usage\n```go\ncolumns, _ := client.Board(1).GetColumns(ctx)\ntask, _ := client.Board(1).CreateTask(ctx, kanboard.NewTask(\"Title\"))\n```\n\n## Acceptance criteria\n- All methods delegate to direct Client methods\n- Proper error propagation","status":"open","priority":1,"issue_type":"feature","owner":"mail@oliverjakoubek.de","created_at":"2026-01-15T17:35:40.044649709+01:00","created_by":"Oliver Jakoubek","updated_at":"2026-01-15T17:35:40.044649709+01:00","dependencies":[{"issue_id":"kanboard-api-2ze","depends_on_id":"kanboard-api-apl","type":"blocks","created_at":"2026-01-15T17:43:30.81063282+01:00","created_by":"Oliver Jakoubek"},{"issue_id":"kanboard-api-2ze","depends_on_id":"kanboard-api-l9b","type":"blocks","created_at":"2026-01-15T17:43:30.874964284+01:00","created_by":"Oliver Jakoubek"},{"issue_id":"kanboard-api-2ze","depends_on_id":"kanboard-api-0fz","type":"blocks","created_at":"2026-01-15T17:43:30.939377116+01:00","created_by":"Oliver Jakoubek"},{"issue_id":"kanboard-api-2ze","depends_on_id":"kanboard-api-91a","type":"blocks","created_at":"2026-01-15T17:43:31.005026627+01:00","created_by":"Oliver Jakoubek"}]}

tags.go

@@ -0,0 +1,111 @@
+package kanboard
+
+import (
+	"context"
+	"fmt"
+)
+
+// GetTaskTags returns the tags assigned to a task as a map of tagID to tag name.
+func (c *Client) GetTaskTags(ctx context.Context, taskID int) (map[int]string, error) {
+	params := map[string]int{"task_id": taskID}
+
+	// Kanboard returns map[string]string where keys are string tag IDs
+	var result map[string]string
+	if err := c.call(ctx, "getTaskTags", params, &result); err != nil {
+		return nil, fmt.Errorf("getTaskTags: %w", err)
+	}
+
+	// Convert string keys to int
+	tags := make(map[int]string, len(result))
+	for idStr, name := range result {
+		var id int
+		if _, err := fmt.Sscanf(idStr, "%d", &id); err != nil {
+			continue // Skip invalid IDs
+		}
+		tags[id] = name
+	}
+
+	return tags, nil
+}
+
+// SetTaskTags sets the tags for a task, replacing all existing tags.
+// Tags are specified by name. Non-existent tags will be auto-created.
+func (c *Client) SetTaskTags(ctx context.Context, projectID, taskID int, tags []string) error {
+	params := map[string]interface{}{
+		"project_id": projectID,
+		"task_id":    taskID,
+		"tags":       tags,
+	}
+
+	var result bool
+	if err := c.call(ctx, "setTaskTags", params, &result); err != nil {
+		return fmt.Errorf("setTaskTags: %w", err)
+	}
+
+	return nil
+}
+
+// GetAllTags returns all tags in the system.
+func (c *Client) GetAllTags(ctx context.Context) ([]Tag, error) {
+	var result []Tag
+	if err := c.call(ctx, "getAllTags", nil, &result); err != nil {
+		return nil, fmt.Errorf("getAllTags: %w", err)
+	}
+	return result, nil
+}
+
+// GetTagsByProject returns all tags for a specific project.
+func (c *Client) GetTagsByProject(ctx context.Context, projectID int) ([]Tag, error) {
+	params := map[string]int{"project_id": projectID}
+
+	var result []Tag
+	if err := c.call(ctx, "getTagsByProject", params, &result); err != nil {
+		return nil, fmt.Errorf("getTagsByProject: %w", err)
+	}
+	return result, nil
+}
+
+// CreateTag creates a new tag in a project and returns the tag ID.
+func (c *Client) CreateTag(ctx context.Context, projectID int, name, colorID string) (int, error) {
+	params := map[string]interface{}{
+		"project_id": projectID,
+		"tag":        name,
+	}
+	if colorID != "" {
+		params["color_id"] = colorID
+	}
+
+	var result int
+	if err := c.call(ctx, "createTag", params, &result); err != nil {
+		return 0, fmt.Errorf("createTag: %w", err)
+	}
+	return result, nil
+}
+
+// UpdateTag updates an existing tag's name and/or color.
+func (c *Client) UpdateTag(ctx context.Context, tagID int, name, colorID string) error {
+	params := map[string]interface{}{
+		"tag_id": tagID,
+		"tag":    name,
+	}
+	if colorID != "" {
+		params["color_id"] = colorID
+	}
+
+	var result bool
+	if err := c.call(ctx, "updateTag", params, &result); err != nil {
+		return fmt.Errorf("updateTag: %w", err)
+	}
+	return nil
+}
+
+// RemoveTag deletes a tag from the system.
+func (c *Client) RemoveTag(ctx context.Context, tagID int) error {
+	params := map[string]int{"tag_id": tagID}
+
+	var result bool
+	if err := c.call(ctx, "removeTag", params, &result); err != nil {
+		return fmt.Errorf("removeTag: %w", err)
+	}
+	return nil
+}

tags_test.go

@@ -0,0 +1,349 @@
+package kanboard
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestClient_GetTaskTags(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req JSONRPCRequest
+		json.NewDecoder(r.Body).Decode(&req)
+
+		if req.Method != "getTaskTags" {
+			t.Errorf("expected method=getTaskTags, got %s", req.Method)
+		}
+
+		params := req.Params.(map[string]interface{})
+		if params["task_id"].(float64) != 42 {
+			t.Errorf("expected task_id=42, got %v", params["task_id"])
+		}
+
+		// Kanboard returns map[string]string
+		resp := JSONRPCResponse{
+			JSONRPC: "2.0",
+			ID:      req.ID,
+			Result:  json.RawMessage(`{"1": "urgent", "2": "backend", "5": "bug"}`),
+		}
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL).WithAPIToken("test-token")
+
+	tags, err := client.GetTaskTags(context.Background(), 42)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if len(tags) != 3 {
+		t.Errorf("expected 3 tags, got %d", len(tags))
+	}
+	if tags[1] != "urgent" {
+		t.Errorf("expected tags[1]='urgent', got %s", tags[1])
+	}
+	if tags[2] != "backend" {
+		t.Errorf("expected tags[2]='backend', got %s", tags[2])
+	}
+	if tags[5] != "bug" {
+		t.Errorf("expected tags[5]='bug', got %s", tags[5])
+	}
+}
+
+func TestClient_GetTaskTags_Empty(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req JSONRPCRequest
+		json.NewDecoder(r.Body).Decode(&req)
+
+		resp := JSONRPCResponse{
+			JSONRPC: "2.0",
+			ID:      req.ID,
+			Result:  json.RawMessage(`{}`),
+		}
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL).WithAPIToken("test-token")
+
+	tags, err := client.GetTaskTags(context.Background(), 42)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if len(tags) != 0 {
+		t.Errorf("expected 0 tags, got %d", len(tags))
+	}
+}
+
+func TestClient_SetTaskTags(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req JSONRPCRequest
+		json.NewDecoder(r.Body).Decode(&req)
+
+		if req.Method != "setTaskTags" {
+			t.Errorf("expected method=setTaskTags, got %s", req.Method)
+		}
+
+		params := req.Params.(map[string]interface{})
+		if params["project_id"].(float64) != 1 {
+			t.Errorf("expected project_id=1, got %v", params["project_id"])
+		}
+		if params["task_id"].(float64) != 42 {
+			t.Errorf("expected task_id=42, got %v", params["task_id"])
+		}
+
+		tags := params["tags"].([]interface{})
+		if len(tags) != 2 {
+			t.Errorf("expected 2 tags, got %d", len(tags))
+		}
+
+		resp := JSONRPCResponse{
+			JSONRPC: "2.0",
+			ID:      req.ID,
+			Result:  json.RawMessage(`true`),
+		}
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL).WithAPIToken("test-token")
+
+	err := client.SetTaskTags(context.Background(), 1, 42, []string{"urgent", "backend"})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestClient_SetTaskTags_Empty(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req JSONRPCRequest
+		json.NewDecoder(r.Body).Decode(&req)
+
+		params := req.Params.(map[string]interface{})
+		tags := params["tags"].([]interface{})
+		if len(tags) != 0 {
+			t.Errorf("expected 0 tags, got %d", len(tags))
+		}
+
+		resp := JSONRPCResponse{
+			JSONRPC: "2.0",
+			ID:      req.ID,
+			Result:  json.RawMessage(`true`),
+		}
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL).WithAPIToken("test-token")
+
+	// Clear all tags by passing empty slice
+	err := client.SetTaskTags(context.Background(), 1, 42, []string{})
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestClient_GetAllTags(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req JSONRPCRequest
+		json.NewDecoder(r.Body).Decode(&req)
+
+		if req.Method != "getAllTags" {
+			t.Errorf("expected method=getAllTags, got %s", req.Method)
+		}
+
+		resp := JSONRPCResponse{
+			JSONRPC: "2.0",
+			ID:      req.ID,
+			Result:  json.RawMessage(`[{"id": "1", "name": "urgent", "project_id": "1", "color_id": "red"}]`),
+		}
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL).WithAPIToken("test-token")
+
+	tags, err := client.GetAllTags(context.Background())
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if len(tags) != 1 {
+		t.Errorf("expected 1 tag, got %d", len(tags))
+	}
+	if tags[0].Name != "urgent" {
+		t.Errorf("expected name='urgent', got %s", tags[0].Name)
+	}
+}
+
+func TestClient_GetTagsByProject(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req JSONRPCRequest
+		json.NewDecoder(r.Body).Decode(&req)
+
+		if req.Method != "getTagsByProject" {
+			t.Errorf("expected method=getTagsByProject, got %s", req.Method)
+		}
+
+		params := req.Params.(map[string]interface{})
+		if params["project_id"].(float64) != 5 {
+			t.Errorf("expected project_id=5, got %v", params["project_id"])
+		}
+
+		resp := JSONRPCResponse{
+			JSONRPC: "2.0",
+			ID:      req.ID,
+			Result:  json.RawMessage(`[{"id": "1", "name": "urgent", "project_id": "5", "color_id": "red"}]`),
+		}
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL).WithAPIToken("test-token")
+
+	tags, err := client.GetTagsByProject(context.Background(), 5)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if len(tags) != 1 {
+		t.Errorf("expected 1 tag, got %d", len(tags))
+	}
+}
+
+func TestClient_CreateTag(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req JSONRPCRequest
+		json.NewDecoder(r.Body).Decode(&req)
+
+		if req.Method != "createTag" {
+			t.Errorf("expected method=createTag, got %s", req.Method)
+		}
+
+		params := req.Params.(map[string]interface{})
+		if params["project_id"].(float64) != 1 {
+			t.Errorf("expected project_id=1, got %v", params["project_id"])
+		}
+		if params["tag"] != "new-tag" {
+			t.Errorf("expected tag='new-tag', got %v", params["tag"])
+		}
+		if params["color_id"] != "blue" {
+			t.Errorf("expected color_id='blue', got %v", params["color_id"])
+		}
+
+		resp := JSONRPCResponse{
+			JSONRPC: "2.0",
+			ID:      req.ID,
+			Result:  json.RawMessage(`42`),
+		}
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL).WithAPIToken("test-token")
+
+	tagID, err := client.CreateTag(context.Background(), 1, "new-tag", "blue")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	if tagID != 42 {
+		t.Errorf("expected tagID=42, got %d", tagID)
+	}
+}
+
+func TestClient_CreateTag_NoColor(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req JSONRPCRequest
+		json.NewDecoder(r.Body).Decode(&req)
+
+		params := req.Params.(map[string]interface{})
+		if _, exists := params["color_id"]; exists {
+			t.Error("color_id should not be present when empty")
+		}
+
+		resp := JSONRPCResponse{
+			JSONRPC: "2.0",
+			ID:      req.ID,
+			Result:  json.RawMessage(`42`),
+		}
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL).WithAPIToken("test-token")
+
+	_, err := client.CreateTag(context.Background(), 1, "new-tag", "")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestClient_UpdateTag(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req JSONRPCRequest
+		json.NewDecoder(r.Body).Decode(&req)
+
+		if req.Method != "updateTag" {
+			t.Errorf("expected method=updateTag, got %s", req.Method)
+		}
+
+		params := req.Params.(map[string]interface{})
+		if params["tag_id"].(float64) != 5 {
+			t.Errorf("expected tag_id=5, got %v", params["tag_id"])
+		}
+		if params["tag"] != "updated-name" {
+			t.Errorf("expected tag='updated-name', got %v", params["tag"])
+		}
+
+		resp := JSONRPCResponse{
+			JSONRPC: "2.0",
+			ID:      req.ID,
+			Result:  json.RawMessage(`true`),
+		}
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL).WithAPIToken("test-token")
+
+	err := client.UpdateTag(context.Background(), 5, "updated-name", "green")
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}
+
+func TestClient_RemoveTag(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		var req JSONRPCRequest
+		json.NewDecoder(r.Body).Decode(&req)
+
+		if req.Method != "removeTag" {
+			t.Errorf("expected method=removeTag, got %s", req.Method)
+		}
+
+		params := req.Params.(map[string]interface{})
+		if params["tag_id"].(float64) != 5 {
+			t.Errorf("expected tag_id=5, got %v", params["tag_id"])
+		}
+
+		resp := JSONRPCResponse{
+			JSONRPC: "2.0",
+			ID:      req.ID,
+			Result:  json.RawMessage(`true`),
+		}
+		json.NewEncoder(w).Encode(resp)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL).WithAPIToken("test-token")
+
+	err := client.RemoveTag(context.Background(), 5)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+}