feat(tools): add tool for getting label values

Signed-off-by: TJ Hoplock <[email protected]>

Author: tjhop

pkg/mcp/promapi.go

@@ -187,6 +187,30 @@ func labelNamesApiCall(ctx context.Context, matchers []string, start, end time.T
 	return string(jsonBytes), nil
 }
 
+func labelValuesApiCall(ctx context.Context, label string, matchers []string, start, end time.Time) (string, error) {
+	result, warnings, err := apiV1Client.LabelValues(ctx, label, matchers, start, end)
+	if err != nil {
+		return "", fmt.Errorf("error getting label values: %w", err)
+	}
+
+	lvals := make([]string, len(result))
+	for i, lval := range result {
+		lvals[i] = string(lval)
+	}
+
+	res := queryApiResponse{
+		Result:   strings.Join(lvals, "\n"),
+		Warnings: warnings,
+	}
+
+	jsonBytes, err := json.Marshal(res)
+	if err != nil {
+		return "", fmt.Errorf("error converting label values response to JSON: %w", err)
+	}
+
+	return string(jsonBytes), nil
+}
+
 func buildinfoApiCall(ctx context.Context) (string, error) {
 	ctx, cancel := context.WithTimeout(ctx, apiTimeout)
 	defer cancel()

pkg/mcp/server.go

@@ -29,6 +29,7 @@ func NewServer(logger *slog.Logger) *server.MCPServer {
 	mcpServer.AddTool(rangeQueryTool, rangeQueryToolHandler)
 	mcpServer.AddTool(seriesTool, seriesToolHandler)
 	mcpServer.AddTool(labelNamesTool, labelNamesToolHandler)
+	mcpServer.AddTool(labelValuesTool, labelValuesToolHandler)
 	mcpServer.AddTool(tsdbStatsTool, tsdbStatsToolHandler)
 	mcpServer.AddTool(listAlertsTool, listAlertsToolHandler)
 	mcpServer.AddTool(alertmanagersTool, alertmanagersToolHandler)

pkg/mcp/tools.go

@@ -36,7 +36,6 @@ var (
 				" Must be either Unix timestamp or RFC3339. Defaults to 5m ago."),
 		),
 		mcp.WithString("end_time",
-			mcp.Required(),
 			mcp.Description("[Optional] End timestamp for the query to be executed at."+
 				" Must be either Unix timestamp or RFC3339. Defaults to current time."),
 		),
@@ -57,7 +56,6 @@ var (
 				" Must be either Unix timestamp or RFC3339. Defaults to 5m ago."),
 		),
 		mcp.WithString("end_time",
-			mcp.Required(),
 			mcp.Description("[Optional] End timestamp for the query to be executed at."+
 				" Must be either Unix timestamp or RFC3339. Defaults to current time."),
 		),
@@ -74,7 +72,26 @@ var (
 				" Must be either Unix timestamp or RFC3339. Defaults to 5m ago."),
 		),
 		mcp.WithString("end_time",
+			mcp.Description("[Optional] End timestamp for the query to be executed at."+
+				" Must be either Unix timestamp or RFC3339. Defaults to current time."),
+		),
+	)
+
+	labelValuesTool = mcp.NewTool("label_values",
+		mcp.WithDescription("Performs a query for the values of the given label, time range and matchers"),
+		mcp.WithString("label",
 			mcp.Required(),
+			mcp.Description("The label to query values for"),
+		),
+		mcp.WithArray("matchers",
+			mcp.Required(),
+			mcp.Description("Label matchers"),
+		),
+		mcp.WithString("start_time",
+			mcp.Description("[Optional] Start timestamp for the query to be executed at."+
+				" Must be either Unix timestamp or RFC3339. Defaults to 5m ago."),
+		),
+		mcp.WithString("end_time",
 			mcp.Description("[Optional] End timestamp for the query to be executed at."+
 				" Must be either Unix timestamp or RFC3339. Defaults to current time."),
 		),
@@ -261,6 +278,49 @@ func labelNamesToolHandler(ctx context.Context, request mcp.CallToolRequest) (*m
 	return mcp.NewToolResultText(data), err
 }
 
+// LabelValues performs a query for the values of the given label, time range and matchers.
+func labelValuesToolHandler(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	arguments := request.Params.Arguments
+	label, ok := arguments["label"].(string)
+	if !ok {
+		return nil, errors.New("label must be a string")
+	}
+
+	argMatchers, ok := arguments["matchers"].([]any)
+	if !ok {
+		return nil, errors.New("matchers must be an array")
+	}
+
+	matchers := make([]string, len(argMatchers))
+	for i, m := range argMatchers {
+		matchers[i] = m.(string)
+	}
+
+	endTs := time.Now()
+	startTs := endTs.Add(DefaultLookbackDelta)
+
+	if argEndTime, ok := arguments["end_time"].(string); ok {
+		parsedEndTime, err := mcpProm.ParseTimestamp(argEndTime)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse end_time %s from args: %w", argEndTime, err)
+		}
+
+		endTs = parsedEndTime
+	}
+
+	if argStartTime, ok := arguments["start_time"].(string); ok {
+		parsedStartTime, err := mcpProm.ParseTimestamp(argStartTime)
+		if err != nil {
+			return nil, fmt.Errorf("failed to parse start_time %s from args: %w", argStartTime, err)
+		}
+
+		startTs = parsedStartTime
+	}
+
+	data, err := labelValuesApiCall(ctx, label, matchers, startTs, endTs)
+	return mcp.NewToolResultText(data), err
+}
+
 func listAlertsToolHandler(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
 	data, err := listAlertsApiCall(ctx)
 	return mcp.NewToolResultText(data), err