diff --git a/AGENTS.md b/AGENTS.md
index 0f50882..55fad39 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -24,7 +24,7 @@ lua test/test_formatter.lua  # Run formatter tests
 lua test/test_plc_json.lua   # Run plc_json tests
 
 # Reference Project
-# Tests use files from: ~/dev/siemens/projects/scl_lang_support_lazyvim_ref_project/
+# Tests use files from: ~/Documents/siemens/scl_lang_support_lazyvim_ref_project/
 # Override with: SCL_REF_PROJECT=/path/to/ref lua tests/run_tests.lua
 ```
 
@@ -152,7 +152,7 @@ The LSP validates data types and provides warnings for unknown types:
 
 Use the reference project for testing:
 ```
-~/dev/siemens/projects/scl_lang_support_lazyvim_ref_project/
+~/Documenta/siemens/scl_lang_support_lazyvim_ref_project/
 ```
 
 Contains `.scl`, `.db`, `.udt`, and `.xml` files for comprehensive testing of:
diff --git a/src/main.lua b/src/main.lua
index fd0c0cf..fb7b2b9 100644
--- a/src/main.lua
+++ b/src/main.lua
@@ -717,6 +717,72 @@ function handlers.textDocument_hover(params)
 	return nil
 end
 
+--- Detect if cursor is inside a function call's parentheses
+--- Scans backwards from cursor to find an unmatched ( and returns the name before it
+--- @param line string The current line content
+--- @param col number Cursor column (0-indexed LSP position)
+--- @return string|nil Function/block name, or nil if not in a call context
+local function get_call_context(line, col)
+	if col <= 1 then return nil end
+	local before_cursor = line:sub(1, col)
+	local paren_pos = nil
+	for i = #before_cursor, 1, -1 do
+		local c = before_cursor:sub(i, i)
+		if c == ")" then break end
+		if c == "(" then paren_pos = i; break end
+	end
+	if not paren_pos then return nil end
+	local before_paren = before_cursor:sub(1, paren_pos - 1)
+	return before_paren:match("([%w_]+)%s*$")
+end
+
+--- Resolve a function/variable call name to its parameter info
+--- Checks variables (for data_type resolution), built-in parameters, and workspace types
+--- @param call_name string The name to resolve (e.g., "instTestTimer" or "TON")
+--- @param variables table|nil Document variables table
+--- @param types table|nil Document types table
+--- @return table|nil Parameter definition with inputs and outputs arrays, or nil
+local function resolve_call_params(call_name, variables, types)
+	if not call_name then return nil end
+	local clean_name = call_name:gsub("^#", "")
+	local data_type = variables and variables[clean_name] and variables[clean_name].data_type
+	local resolved_name = data_type or clean_name
+	local builtin_params = builtin.get_parameters(resolved_name)
+	if builtin_params then return builtin_params end
+	local type_info = types and types[resolved_name]
+	if type_info and type_info.fields then
+		return { inputs = type_info.fields, outputs = {} }
+	end
+	return nil
+end
+
+local function add_param_items(items, params, prefix_filter)
+	for _, inp in ipairs(params.inputs or {}) do
+		local label = inp.name .. " := "
+		if prefix_filter == "" or inp.name:upper():find("^" .. prefix_filter:upper(), 1, true) then
+			table.insert(items, {
+				label = label,
+				kind = 13,
+				detail = "Parameter (" .. (inp.type or "ANY") .. ")",
+				insertText = inp.name .. " := ",
+				insertTextFormat = 1,
+			})
+		end
+	end
+	for _, out in ipairs(params.outputs or {}) do
+		local label = out.name .. " => "
+		if prefix_filter == "" or out.name:upper():find("^" .. prefix_filter:upper(), 1, true) then
+			table.insert(items, {
+				label = label,
+				kind = 13,
+				detail = "Output (" .. (out.type or "ANY") .. ")",
+				insertText = out.name .. " => ",
+				insertTextFormat = 1,
+			})
+		end
+	end
+end
+
 --- Handle textDocument/completion request
 --- Provides completion items based on context (VAR section, member access, etc.)
 --- @param params table Contains textDocument with uri and position
@@ -738,7 +804,7 @@ function handlers.textDocument_completion(params)
 	if line_idx <= #lines then
 		local line = lines[line_idx]
 		local col = params.position.character
-		local trigger = col > 0 and line:sub(col, col) or ""
+		local trigger = (params.context and params.context.triggerCharacter) or (col > 0 and line:sub(col, col) or "")
 		local line_before = col > 1 and line:sub(1, col - 1) or ""
 
 		-- Get word prefix being typed (for filtering)
@@ -748,29 +814,35 @@ function handlers.textDocument_completion(params)
 		end
 		local word_prefix = line:sub(prefix_start + 1, col - 1)
 
-		-- Check if we're in VAR section
+		-- Check if typing after # prefix (e.g., #myVar)
+		local has_hash_prefix = line_before:match("#[%w_]*$")
+
+		-- Check if we're in VAR section (detects all VAR variants)
 		local in_var_section = false
 		for i = line_idx - 1, 1, -1 do
 			local prev_line = lines[i]:gsub("^%s+", ""):gsub("%s+$", "")
-			if prev_line:match("^END_VAR") or prev_line:match("^VAR_TEMP") or prev_line:match("^VAR_IN_OUT") or prev_line:match("^VAR_OUTPUT") or prev_line:match("^VAR_INPUT") then
+			if prev_line:match("^END_VAR") then
 				break
 			end
-			if prev_line:match("^VAR%s*$") or prev_line:match("^VAR$") then
+			if prev_line:match("^VAR") then
 				in_var_section = true
 				break
 			end
 		end
 
-		if trigger == "#" then
+		if trigger == "#" or has_hash_prefix then
 			if doc.variables then
+				local prefix = has_hash_prefix and line_before:match("#([%w_]*)$") or word_prefix
 				for name, info in pairs(doc.variables) do
-					table.insert(items, {
-						label = "#" .. name,
-						kind = 13,
-						detail = "Local variable (" .. (info.type or "unknown") .. ")",
-						insertText = "#" .. name,
-						insertTextFormat = 1,
-					})
+					if prefix == "" or name:upper():find("^" .. prefix:upper(), 1, true) then
+						table.insert(items, {
+							label = "#" .. name,
+							kind = 13,
+							detail = "Variable (" .. (info.type or "VAR") .. "): " .. (info.data_type or "unknown"),
+							insertText = "#" .. name,
+							insertTextFormat = 1,
+						})
+					end
 				end
 			end
 		elseif trigger == "." then
@@ -837,7 +909,16 @@ function handlers.textDocument_completion(params)
 				end
 			end
 		elseif trigger == "(" then
-			if doc.functions then
+			-- Try get_call_context first (handles case where ( is already in the line)
+			local call_name = get_call_context(line, col)
+			-- Fallback: ( may not be in the line yet (client sends completion before didChange)
+			if not call_name and col > 0 then
+				call_name = line:sub(1, col):match("([%w_]+)%s*$")
+			end
+			local params = call_name and resolve_call_params(call_name, doc.variables, doc.types)
+			if params then
+				add_param_items(items, params, "")
+			elseif doc.functions then
 				for _, func in ipairs(doc.functions) do
 					table.insert(items, {
 						label = func.name,
@@ -849,6 +930,10 @@ function handlers.textDocument_completion(params)
 				end
 			end
 		else
+			-- Check if we're inside a function call (e.g., after instTestTimer()
+			local call_name = get_call_context(line, col)
+			local call_params = call_name and resolve_call_params(call_name, doc.variables, doc.types)
+
 			-- Check context before cursor
 			local is_var_decl = line_before:match(":%s*$")
 
@@ -881,6 +966,26 @@ function handlers.textDocument_completion(params)
 						add_item(type_name, 7, type_info.kind or "Type")
 					end
 				end
+
+				-- Add declared variables (without # prefix in label, insert with #)
+				if doc.variables then
+					for name, info in pairs(doc.variables) do
+						if word_prefix == "" or name:upper():find("^" .. word_prefix:upper(), 1, true) then
+							table.insert(items, {
+								label = "#" .. name,
+								kind = 13,
+								detail = "Variable (" .. (info.type or "VAR") .. "): " .. (info.data_type or "unknown"),
+								insertText = "#" .. name,
+								insertTextFormat = 1,
+							})
+						end
+					end
+				end
+
+				-- Add function/block call parameters if inside (...) context
+				if call_params then
+					add_param_items(items, call_params, word_prefix)
+				end
 			else
 				-- General context: show all
 				for type_name, _ in pairs(builtin.DATA_TYPES) do
@@ -894,6 +999,26 @@ function handlers.textDocument_completion(params)
 				for func_name, _ in pairs(builtin.FUNCTIONS) do
 					add_item(func_name, 3, "Function")
 				end
+
+				-- Add declared variables in general context too
+				if doc.variables then
+					for name, info in pairs(doc.variables) do
+						if word_prefix == "" or name:upper():find("^" .. word_prefix:upper(), 1, true) then
+							table.insert(items, {
+								label = "#" .. name,
+								kind = 13,
+								detail = "Variable (" .. (info.type or "VAR") .. "): " .. (info.data_type or "unknown"),
+								insertText = "#" .. name,
+								insertTextFormat = 1,
+							})
+						end
+					end
+				end
+
+				-- Add function/block call parameters if inside (...) context
+				if call_params then
+					add_param_items(items, call_params, word_prefix)
+				end
 			end
 		end
 	end