Langfuse MCP Server

Instructions

Input Schema

Input Schema (JSON Schema)

Implementation Reference

• src/tools/get-cost-analysis.ts:15-193 (handler)

  The main handler function that executes the get_cost_analysis tool. It fetches daily metrics from Langfuse, computes total cost, model breakdown, user breakdown, and daily breakdown, then returns formatted JSON response.
  export async function getCostAnalysis( client: LangfuseAnalyticsClient, args: z.infer<typeof getCostAnalysisSchema> ) { const filters: any[] = []; if (args.environment) { filters.push({ column: 'environment', operator: 'equals', value: args.environment, type: 'string', }); } // Calculate total cost from daily data (which works correctly) let totalCost = 0; let dailyData: any[] = []; // Get daily data first since it's working correctly try { const dailyResponse = await client.getDailyMetrics({ tags: args.environment ? [`environment:${args.environment}`] : undefined, }); if (dailyResponse.data && Array.isArray(dailyResponse.data)) { // Filter by date range and calculate total const fromDate = new Date(args.from); const toDate = new Date(args.to); dailyData = dailyResponse.data.filter((day: any) => { const dayDate = new Date(day.date); return dayDate >= fromDate && dayDate <= toDate; }); // Calculate total cost from working daily data totalCost = dailyData.reduce((sum: number, day: any) => { return sum + (day.totalCost || 0); }, 0); } } catch (error) { console.error('Error getting daily data for total calculation:', error); } const result: CostAnalysis = { projectId: client.getProjectId(), from: args.from, to: args.to, totalCost, breakdown: {}, }; // Model breakdown - extract from working daily data if (args.includeModelBreakdown) { try { const modelMap = new Map<string, { cost: number; tokens: number; observations: number; }>(); // Aggregate model data from daily breakdown (which works correctly) dailyData.forEach((day: any) => { if (day.usage && Array.isArray(day.usage)) { day.usage.forEach((usage: any) => { const modelName = usage.model || 'unknown'; const existing = modelMap.get(modelName) || { cost: 0, tokens: 0, observations: 0 }; modelMap.set(modelName, { cost: existing.cost + (usage.totalCost || 0), tokens: existing.tokens + (usage.totalUsage || usage.inputUsage + usage.outputUsage || 0), observations: existing.observations + (usage.countObservations || 0), }); }); } }); const modelBreakdown = Array.from(modelMap.entries()).map(([model, data]) => ({ model, cost: data.cost, tokens: data.tokens, observations: data.observations, percentage: totalCost > 0 ? Math.round((data.cost / totalCost) * 100 * 100) / 100 : 0, })); result.breakdown.byModel = modelBreakdown .sort((a, b) => b.cost - a.cost) .slice(0, args.limit); } catch (error) { console.error('Error building model breakdown from daily data:', error); result.breakdown.byModel = []; } } // User breakdown if (args.includeUserBreakdown) { try { const userResponse = await client.getMetrics({ view: 'traces', from: args.from, to: args.to, metrics: [ { measure: 'totalCost', aggregation: 'sum' }, { measure: 'totalTokens', aggregation: 'sum' }, { measure: 'count', aggregation: 'count' }, ], dimensions: [{ field: 'userId' }], filters, }); const userBreakdown: Array<{ userId: string; cost: number; tokens: number; traces: number; percentage: number; }> = []; if (userResponse.data && Array.isArray(userResponse.data)) { userResponse.data.forEach((row: any, index: number) => { if (row.userId) { // Use correct field names from metrics API response const cost = row.totalCost_sum || 0; userBreakdown.push({ userId: row.userId, cost, tokens: row.totalTokens_sum || 0, traces: row.count_count || 0, percentage: totalCost > 0 ? Math.round((cost / totalCost) * 100 * 100) / 100 : 0, }); } }); } result.breakdown.byUser = userBreakdown .sort((a, b) => b.cost - a.cost) .slice(0, args.limit); } catch (error) { console.error('Error fetching user breakdown:', error); result.breakdown.byUser = []; } } // Daily breakdown - reuse the daily data we already fetched if (args.includeDailyBreakdown) { try { const dailyBreakdown = dailyData.map((day: any) => { // Calculate total tokens from usage breakdown let totalTokens = 0; if (day.usage && Array.isArray(day.usage)) { totalTokens = day.usage.reduce((sum: number, usage: any) => { return sum + (usage.totalUsage || usage.inputUsage + usage.outputUsage || 0); }, 0); } return { date: day.date, cost: day.totalCost || 0, tokens: totalTokens, traces: day.countTraces || 0, }; }); result.breakdown.byDay = dailyBreakdown.sort((a, b) => new Date(a.date).getTime() - new Date(b.date).getTime() ); } catch (error) { console.error('Error building daily breakdown:', error); result.breakdown.byDay = []; } } return { content: [ { type: 'text' as const, text: JSON.stringify(result, null, 2), }, ], }; }
• src/tools/get-cost-analysis.ts:5-13 (schema)

  Zod schema defining the input parameters for the get_cost_analysis tool, used for validation in the dispatcher.
  export const getCostAnalysisSchema = z.object({ from: z.string().datetime(), to: z.string().datetime(), environment: z.string().optional(), includeModelBreakdown: z.boolean().default(true), includeUserBreakdown: z.boolean().default(true), includeDailyBreakdown: z.boolean().default(true), limit: z.number().min(5).max(100).default(20), });
• src/index.ts:455-496 (registration)

  Tool registration object in the listTools handler's allTools array, providing name, description, and input schema for MCP tool discovery.
  { name: 'get_cost_analysis', description: 'Specialized cost breakdowns by model, user, and daily trends.', inputSchema: { type: 'object', properties: { from: { type: 'string', format: 'date-time', description: 'Start timestamp (ISO 8601)', }, to: { type: 'string', format: 'date-time', description: 'End timestamp (ISO 8601)', }, environment: { type: 'string', description: 'Optional environment filter', }, includeModelBreakdown: { type: 'boolean', description: 'Include breakdown by model (default: true)', }, includeUserBreakdown: { type: 'boolean', description: 'Include breakdown by user (default: true)', }, includeDailyBreakdown: { type: 'boolean', description: 'Include daily breakdown (default: true)', }, limit: { type: 'number', minimum: 5, maximum: 100, description: 'Maximum items per breakdown (default: 20)', }, }, required: ['from', 'to'], }, },
• src/index.ts:1051-1054 (registration)

  Dispatch case in the CallToolRequestSchema handler that validates input with the schema and invokes the handler function.
  case 'get_cost_analysis': { const args = getCostAnalysisSchema.parse(request.params.arguments); return await getCostAnalysis(this.client, args); }