feat(tools): add tool for getting metric metadata

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

Author: tjhop

pkg/mcp/promapi.go

@@ -313,6 +313,23 @@ func targetsMetadataApiCall(ctx context.Context, matchTarget, metric, limit stri
 	return string(jsonBytes), nil
 }
 
+func metricMetadataApiCall(ctx context.Context, metric, limit string) (string, error) {
+	ctx, cancel := context.WithTimeout(ctx, apiTimeout)
+	defer cancel()
+
+	mm, err := apiV1Client.Metadata(ctx, metric, limit)
+	if err != nil {
+		return "", fmt.Errorf("error getting metric metadata from Prometheus: %w", err)
+	}
+
+	jsonBytes, err := json.Marshal(mm)
+	if err != nil {
+		return "", fmt.Errorf("error converting metric metadata to JSON: %w", err)
+	}
+
+	return string(jsonBytes), nil
+}
+
 func walReplayApiCall(ctx context.Context) (string, error) {
 	ctx, cancel := context.WithTimeout(ctx, apiTimeout)
 	defer cancel()

pkg/mcp/server.go

@@ -40,6 +40,7 @@ func NewServer(logger *slog.Logger) *server.MCPServer {
 	mcpServer.AddTool(rulesTool, rulesToolHandler)
 	mcpServer.AddTool(targetsTool, targetsToolHandler)
 	mcpServer.AddTool(targetsMetadataTool, targetsMetadataToolHandler)
+	mcpServer.AddTool(metricMetadataTool, metricMetadataToolHandler)
 	mcpServer.AddTool(walReplayTool, walReplayToolHandler)
 
 	return mcpServer

pkg/mcp/tools.go

@@ -146,6 +146,16 @@ var (
 		),
 	)
 
+	metricMetadataTool = mcp.NewTool("metric_metadata",
+		mcp.WithDescription("Returns metadata about metrics currently scraped by the metric name."),
+		mcp.WithString("metric",
+			mcp.Description("[Optional] A metric name to retrieve metadata for. All metric metadata is retrieved if left empty."),
+		),
+		mcp.WithString("limit",
+			mcp.Description("[Optional] Maximum number of metrics to return."),
+		),
+	)
+
 	walReplayTool = mcp.NewTool("wal_replay_status",
 		mcp.WithDescription("Get current WAL replay status"),
 	)
@@ -400,6 +410,25 @@ func targetsMetadataToolHandler(ctx context.Context, request mcp.CallToolRequest
 	return mcp.NewToolResultText(data), err
 }
 
+// // Metadata returns metadata about metrics currently scraped by the metric name.
+// Metadata(ctx context.Context, metric, limit string) (map[string][]Metadata, error)
+func metricMetadataToolHandler(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	arguments := request.Params.Arguments
+
+	metric := ""
+	if argMetric, ok := arguments["metric"].(string); ok {
+		metric = argMetric
+	}
+
+	limit := ""
+	if argLimit, ok := arguments["limit"].(string); ok {
+		limit = argLimit
+	}
+
+	data, err := metricMetadataApiCall(ctx, metric, limit)
+	return mcp.NewToolResultText(data), err
+}
+
 func walReplayToolHandler(ctx context.Context, request mcp.CallToolRequest) (*mcp.CallToolResult, error) {
 	data, err := walReplayApiCall(ctx)
 	return mcp.NewToolResultText(data), err