用 n8n 账本追踪 AI Agent 成本与决策

通过 Webhook 接收 Agent 事件 → 计算 token 成本 → 持久化账本 → WhatsApp 预算告警与日报

给谁

运行多 Agent 或 Supervisor 工作流、需要追踪每次 LLM/工具调用成本的技术人员

你会得到

获得按 run、agent、model、tool 汇总的实时成本账本，超预算时 WhatsApp 告警，每日定时摘要

你需要

n8n · whatsapp

步骤

1. 导入模板

   在 n8n 中打开模板页面，导入「Track AI agent costs and decisions via webhooks and WhatsApp digests」工作流。导入后可见两个主要分支：Record Events（事件记录）与 Report & Daily Digest（报告与日报）。

2. 配置凭证与常量

   1) 在 WhatsApp Business Cloud 节点关联你的 WhatsApp Business 凭证，填写 whatsappBusinessPhoneId（WhatsApp 电话号码 ID）与 whatsappRecipientPhone（接收告警的手机号）。 2) 编辑 Ledger Config 节点：设置 per-run 预算（runBudgetUsd，默认 0.5）、单条 run 最大条目数（maxEntries，默认 5000）、最大保留 run 数（maxRuns，默认 200）、每百万 token 定价表（pricingPerMillionUsd，JSON 格式，默认含 default/claude-haiku/claude-sonnet/claude-opus 四档）。 3) 编辑 Report Config 节点：设置日报时间窗口（digestWindowHours，默认 24）、最近条目限制（recentLimit，默认 20）、以及 WhatsApp 发送目标 ID。

3. 激活并获取 Webhook URL

   激活工作流（Active）。只有激活后，static data 才会在每次执行后持久化保存。复制两个 Webhook 路径的完整 URL： - POST /webhook/agent-ledger-event（接收事件） - GET /webhook/agent-ledger-report（查询报告） 将 POST URL 配置到你的 Agent 或 Supervisor 工作流中，在每次 LLM 调用、工具调用或决策后发送事件。

4. 发送 Agent 事件到账本

   向 POST 端点发送事件。支持单条对象或 events 数组批量发送。每条事件需包含 runId、agentName、eventType（llm_call/tool_call/decision/error）。对于 llm_call，提供 model、inputTokens、outputTokens；对于 tool_call，提供 toolName，可选 toolCostUsd；对于 decision，提供 decision 字段。来源中的 Validate and Price Events 节点会校验字段、按 pricingPerMillionUsd 计算成本（或接受显式 costUsd），随后 Append to Ledger 节点将事件写入 static data，更新 per-run 汇总，并在超预算时触发一次性 WhatsApp 告警。

   运行提示词 · 来源原文。Validate and Price Events 节点的 JS Code 字段

   复制提示词

   const cfg = $input.first().json;
   const body = cfg.body || {};
   
   let pricing;
   try { pricing = JSON.parse(cfg.pricingPerMillionUsd); } catch (e) { pricing = { default: { input: 3, output: 15 } }; }
   
   const TYPES = ['tool_call', 'decision', 'llm_call', 'error'];
   const raw = Array.isArray(body.events) ? body.events : (body.eventType ? [body] : []);
   const errors = [];
   const events = [];
   const num = v => (Number(v) > 0 ? Number(v) : 0);
   const preview = v => v === undefined || v === null ? null : (typeof v === 'string' ? v : JSON.stringify(v)).slice(0, 500);
   
   function rateFor(model) {
     const keys = Object.keys(pricing)
       .filter(k => k !== 'default' && String(model || '').startsWith(k))
       .sort((a, b) => b.length - a.length);
     return pricing[keys[0]] || pricing.default || { input: 0, output: 0 };
   }
   
   if (raw.length === 0) errors.push('Body must contain an events array or a single event with eventType');
   
   raw.forEach((e, i) => {
     const p = 'events[' + i + ']';
     if (!e || typeof e !== 'object') { errors.push(p + ' must be an object'); return; }
     if (!e.runId) errors.push(p + ' is missing runId');
     if (!TYPES.includes(e.eventType)) errors.push(p + ' eventType must be one of ' + TYPES.join(', '));
     if (e.eventType === 'tool_call' && !e.toolName) errors.push(p + ' tool_call requires toolName');
     if (e.eventType === 'decision' && !e.decision) errors.push(p + ' decision requires decision');
   
     const inTok = num(e.inputTokens), outTok = num(e.outputTokens), cacheTok = num(e.cacheReadTokens);
     const r = rateFor(e.model);
     const cacheRate = r.cacheRead !== undefined ? r.cacheRead : (r.input || 0) * 0.1;
     const tokenCost = inTok / 1e6 * (r.input || 0) + outTok / 1e6 * (r.output || 0) + cacheTok / 1e6 * cacheRate;
     const explicit = e.costUsd !== undefined && Number(e.costUsd) >= 0 ? Number(e.costUsd) : null;
     const costUsd = explicit !== null ? explicit : tokenCost + num(e.toolCostUsd);
   
     events.push({
       runId: e.runId,
       taskId: e.taskId || null,
       agentName: e.agentName || 'unknown',
       eventType: e.eventType,
       eventTimestamp: e.timestamp || new Date().toISOString(),
       toolName: e.toolName || null,
       toolInput: preview(e.toolInput),
       toolOutput: preview(e.toolOutput),
       model: e.model || null,
       decision: e.decision || null,
       reasoning: e.reasoning ? String(e.reasoning).slice(0, 1000) : null,
       confidence: typeof e.confidence === 'number' ? e.confidence : null,
       status: e.status || (e.eventType === 'error' ? 'failed' : 'ok'),
       errorMessage: e.errorMessage ? String(e.errorMessage).slice(0, 500) : null,
       inputTokens: inTok,
       outputTokens: outTok,
       cacheReadTokens: cacheTok,
       latencyMs: num(e.latencyMs),
       costUsd: Math.round(costUsd * 1e6) / 1e6,
       metadata: e.metadata && typeof e.metadata === 'object' ? e.metadata : {}
     });
   });
   
   return [{
     json: {
       valid: errors.length === 0,
       validationError: errors.join('; '),
       events,
       runBudgetUsd: Number(cfg.runBudgetUsd) || 0,
       maxEntries: Number(cfg.maxEntries) || 5000,
       maxRuns: Number(cfg.maxRuns) || 200,
       whatsappBusinessPhoneId: cfg.whatsappBusinessPhoneId,
       whatsappRecipientPhone: cfg.whatsappRecipientPhone
     }
   }];

   运行提示词 · 来源原文。Append to Ledger 节点的 JS Code 字段

   复制提示词

   const s = $input.first().json;
   const sd = $getWorkflowStaticData('global');
   if (!sd.ledger) sd.ledger = { seq: 0, entries: [], runs: {} };
   const L = sd.ledger;
   const now = new Date().toISOString();
   const touched = [];
   const alerts = [];
   let seqFrom = null;
   
   for (const ev of s.events) {
     L.seq += 1;
     if (seqFrom === null) seqFrom = L.seq;
     L.entries.push({ seq: L.seq, id: 'led-' + L.seq, recordedAt: now, ...ev });
   
     const r = L.runs[ev.runId] || (L.runs[ev.runId] = {
       runId: ev.runId, taskId: ev.taskId, agents: {}, totalCostUsd: 0,
       inputTokens: 0, outputTokens: 0, llmCalls: 0, toolCalls: 0, decisions: 0, errors: 0,
       firstEventAt: ev.eventTimestamp, lastEventAt: ev.eventTimestamp, budgetAlerted: false
     });
     r.agents[ev.agentName] = (r.agents[ev.agentName] || 0) + 1;
     r.totalCostUsd = Math.round((r.totalCostUsd + ev.costUsd) * 1e6) / 1e6;
     r.inputTokens += ev.inputTokens;
     r.outputTokens += ev.outputTokens;
     if (ev.eventType === 'llm_call') r.llmCalls += 1;
     if (ev.eventType === 'tool_call') r.toolCalls += 1;
     if (ev.eventType === 'decision') r.decisions += 1;
     if (ev.eventType === 'error' || ev.status !== 'ok') r.errors += 1;
     r.lastEventAt = ev.eventTimestamp;
     if (!touched.includes(ev.runId)) touched.push(ev.runId);
   
     if (s.runBudgetUsd > 0 && r.totalCostUsd > s.runBudgetUsd && !r.budgetAlerted) {
       r.budgetAlerted = true;
       alerts.push('Run ' + ev.runId + ' spent $' + r.totalCostUsd.toFixed(4) + ' (budget $' + s.runBudgetUsd.toFixed(2) + ') after ' + (r.llmCalls + r.toolCalls) + ' calls. Last agent: ' + ev.agentName);
     }
   }
   
   // Retention
   if (L.entries.length > s.maxEntries) L.entries = L.entries.slice(-s.maxEntries);
   const ids = Object.keys(L.runs);
   if (ids.length > s.maxRuns) {
     ids.sort((a, b) => String(L.runs[a].lastEventAt).localeCompare(String(L.runs[b].lastEventAt)))
        .slice(0, ids.length - s.maxRuns)
        .forEach(id => { delete L.runs[id]; });
   }
   
   const runs = touched.filter(id => L.runs[id]).map(id => {
     const r = L.runs[id];
     return {
       runId: r.runId, totalCostUsd: r.totalCostUsd, inputTokens: r.inputTokens, outputTokens: r.outputTokens,
       llmCalls: r.llmCalls, toolCalls: r.toolCalls, decisions: r.decisions, errors: r.errors,
       budgetUsd: s.runBudgetUsd || null, budgetExceeded: s.runBudgetUsd > 0 && r.totalCostUsd > s.runBudgetUsd
     };
   });
   
   return [{
     json: {
       budgetAlert: alerts.length > 0,
       whatsappText: '\uD83D\uDEA8 Agent Ledger budget alert\n\n' + alerts.join('\n'),
       whatsappBusinessPhoneId: s.whatsappBusinessPhoneId,
       whatsappRecipientPhone: s.whatsappRecipientPhone,
       webhookResponse: { recorded: s.events.length, seqFrom, seqTo: L.seq, ledgerSize: L.entries.length, runs }
     }
   }];

5. 查询报告与接收日报

   通过 GET /webhook/agent-ledger-report 查询账本，可选参数：?runId=、?agent=、?since=<ISO date>、?limit=。Build Ledger Report 节点会按 agent、tool、model、decision 聚合，返回 totals、byAgent、byTool、byModel、byDecision、topRuns、recentEntries。若请求来自 Webhook，直接返回 JSON；若由 Daily Digest Schedule（默认每天 09:00 cron）触发，则生成 WhatsApp 文本摘要并发送。

   运行提示词 · 来源原文。Build Ledger Report 节点的 JS Code 字段

   复制提示词

   const c = $input.first().json;
   const isWebhook = !!c.headers;
   const q = c.query || {};
   const sd = $getWorkflowStaticData('global');
   const L = sd.ledger || { seq: 0, entries: [], runs: {} };
   const round = n => Math.round(n * 1e6) / 1e6;
   
   let entries = L.entries;
   let windowLabel = 'all recorded history';
   if (!isWebhook) {
     const hours = Number(c.digestWindowHours) || 24;
     const cutoff = Date.now() - hours * 3600000;
     entries = entries.filter(e => new Date(e.recordedAt).getTime() >= cutoff);
     windowLabel = 'last ' + hours + 'h';
   }
   if (q.runId) entries = entries.filter(e => e.runId === q.runId);
   if (q.agent) entries = entries.filter(e => e.agentName === q.agent);
   if (q.since) entries = entries.filter(e => e.recordedAt >= q.since);
   
   const group = keyFn => {
     const m = {};
     for (const e of entries) {
       const k = keyFn(e);
       if (k === null || k === undefined) continue;
       const g = m[k] || (m[k] = { name: k, events: 0, costUsd: 0, inputTokens: 0, outputTokens: 0, errors: 0, totalLatencyMs: 0 });
       g.events += 1;
       g.costUsd += e.costUsd;
       g.inputTokens += e.inputTokens;
       g.outputTokens += e.outputTokens;
       g.totalLatencyMs += e.latencyMs;
       if (e.eventType === 'error' || e.status !== 'ok') g.errors += 1;
     }
     return Object.values(m)
       .map(({ totalLatencyMs, ...g }) => ({ ...g, costUsd: round(g.costUsd), avgLatencyMs: g.events ? Math.round(totalLatencyMs / g.events) : 0 }))
       .sort((a, b) => b.costUsd - a.costUsd);
   };
   
   const byAgent = group(e => e.agentName);
   const byTool = group(e => e.eventType === 'tool_call' ? e.toolName : null);
   const byModel = group(e => e.model);
   const topRuns = group(e => e.runId).slice(0, 5);
   
   const dm = {};
   for (const e of entries.filter(x => x.eventType === 'decision')) {
     const d = dm[e.decision] || (dm[e.decision] = { decision: e.decision, count: 0, confidenceSum: 0, confidenceN: 0 });
     d.count += 1;
     if (typeof e.confidence === 'number') { d.confidenceSum += e.confidence; d.confidenceN += 1; }
   }
   const byDecision = Object.values(dm)
     .map(d => ({ decision: d.decision, count: d.count, avgConfidence: d.confidenceN ? Math.round(d.confidenceSum / d.confidenceN * 100) / 100 : null }))
     .sort((a, b) => b.count - a.count);
   
   const totals = {
     events: entries.length,
     costUsd: round(entries.reduce((a, e) => a + e.costUsd, 0)),
     inputTokens: entries.reduce((a, e) => a + e.inputTokens, 0),
     outputTokens: entries.reduce((a, e) => a + e.outputTokens, 0),
     llmCalls: entries.filter(e => e.eventType === 'llm_call').length,
     toolCalls: entries.filter(e => e.eventType === 'tool_call').length,
     decisions: entries.filter(e => e.eventType === 'decision').length,
     errors: entries.filter(e => e.eventType === 'error' || e.status !== 'ok').length
   };
   totals.errorRate = totals.events ? Math.round(totals.errors / totals.events * 1000) / 1000 : 0;
   
   const limit = Number(q.limit) || Number(c.recentLimit) || 20;
   const recentEntries = entries.slice(-limit).reverse();
   
   const report = {
     generatedAt: new Date().toISOString(),
     window: windowLabel,
     filters: { runId: q.runId || null, agent: q.agent || null, since: q.since || null },
     totals, byAgent, byTool, byModel, byDecision, topRuns, recentEntries,
     runSummaries: q.runId && L.runs[q.runId] ? L.runs[q.runId] : undefined
   };
   
   const top = arr => arr.length ? arr[0].name + ' ($' + arr[0].costUsd.toFixed(4) + ')' : 'n/a';
   const whatsappText = '\uD83D\uDCD2 Agent Ledger digest (' + windowLabel + ')\n'
     + 'Events: ' + totals.events + ' | LLM calls: ' + totals.llmCalls + ' | Tool calls: ' + totals.toolCalls + ' | Decisions: ' + totals.decisions + '\n'
     + 'Total cost: $' + totals.costUsd.toFixed(4) + ' | Errors: ' + totals.errors + '\n'
     + 'Top agent: ' + top(byAgent) + '\n'
     + 'Top tool: ' + top(byTool) + '\n'
     + 'Top model: ' + top(byModel) + '\n'
     + 'Costliest run: ' + top(topRuns);
   
   return [{ json: { isWebhook, report, whatsappText, whatsappBusinessPhoneId: c.whatsappBusinessPhoneId, whatsappRecipientPhone: c.whatsappRecipientPhone } }];

你是一个 n8n 模板搭建助手。用户希望复现「Track AI agent costs and decisions via webhooks and WhatsApp digests」工作流。请按以下顺序协助：
1. 确认用户已有 n8n 实例和 WhatsApp Business 凭证；
2. 指导导入模板并检查 Ledger Config / Report Config 中的预算、定价、保留限制；
3. 提醒激活工作流后 static data 才会持久化；
4. 提供 POST / GET webhook URL 的复制位置；
5. 给出事件 JSON 样例供测试。