TECHDEV 建立 aibill CLI，按工具呼叫追蹤智能體成本

I can tell you my AI bill to the cent. Ask me which tool call caused it and I used to shrug.

Last week I stared at my provider dashboard: a clean per-key total, zero line items. Which MCP tool ate the budget? Which framework surface did the agent re-read forty times? Was that "heavy" framework actually heavy for my workload? The dashboard had no answers. Hacker News had opinions - 215 points on ChatGPT/Codex limit merges, 291 on the AI cost of JavaScript frameworks. One dev.to author cut their MCP server from 15 tools to 4 by hand-counting tokens with tiktoken. All vibes. No receipts.

So I built the receipt: aibill, a small CLI that reads your real agent session transcripts and attributes tokens and estimated USD to every tool call.

What it does

Four commands, one idea: measure first, cut second, verify third.

aibill scan ~/.claude/projects/my-project/

TOOL                   CALLS   MEAN TOK   P95 TOK   TOTAL TOK       USD*
------------------------------------------------------------------------
mcp__doc_lookup           30     23,265    26,947     697,938     $16.55
mcp__codebase_search      24     15,427    18,889     370,241      $7.81
...

aibill scan parses Claude Code session JSONL (or a generic MCP tool-call JSONL you feed it) and prints per-tool rows - call counts, mean and p95 tokens, totals, USD - plus per-model and per-framework-surface breakdowns. aibill cut --top 3 then suggests cut candidates: duplicated calls with identical inputs, tools whose huge outputs were never referenced again, costly one-shot tools. Candidates, not autopilot - it changes nothing on its own.

Then the part I actually wanted: aibill diff --before old.jsonl --after new.jsonl measures the before/after. On the demo run: 137 calls, 1,425,208 tokens, $31.68 estimated, one doc-lookup tool eating 52% of the bill. After trimming the obvious waste: -49.0% tokens, -52.3% USD - measured on the two transcripts, not promised about your future. aibill budget --max-usd 20 exits non-zero when projected spend exceeds the cap, so the same check runs in CI.

(The GIF runs on synthetic seeded fixtures - run scan on your own transcripts for real numbers.)

The honest fine print

USD is an estimate from public rate cards (verified 2026-11-02, sources in src/pricing.ts), not your invoice. Discounts, caching, tiers and regional multipliers change the real number. Unknown models price at $0 and get flagged, never guessed. Bring contracted rates with --pricing-file.
Claude Code logs token usage per message, so when one message carries several tool calls the usage is split evenly and flagged as shared attribution in the report.
aibill measures. It does not reduce tokens, rewrite prompts, or compress anything. Any "% saved" you see from diff was measured on the two transcripts you gave it.
It reads local transcripts only - never calls billing APIs, never touches credentials, never sends anything anywhere. Transcripts contain your proprietary code; the tool is 100% offline by design. Zero runtime dependencies, Node 20+.

Where rivals beat us

The AWS "MCP Token Cost" piece measures something aibill does not: the upfront tool-schema/context tax - 55k tokens just to describe GitHub MCP's 93 tools before a single call happens. aibill attributes per-call tokens from transcripts; it is blind to that schema tax. The two are complementary: use their number for "should this MCP server be connected at all", use aibill for "now that it is, which 3 calls are eating the bill." Provider dashboards win on authoritative totals; hand-rolled tiktoken audits win on nothing except proving the demand is real.

Try it

Install from source for now (aibill-cli isn't on npm yet - publish pending):

git clone https://github.com/techdevfun/aibill.git
cd aibill && npm install -g .
aibill scan <your-transcript.jsonl>

The point was never the $31. It's that every cost conversation about coding agents is currently vibes - headline benchmarks measured on someone else's workload, gut-feel tool cuts, surprise limit changes. A receipt won't make the bill smaller by itself. But at least now you can argue with it.

Repo: https://github.com/techdevfun/aibill - MIT, issues and redacted-transcript bug reports welcome.