Cost Tracking
Use this skill to analyze Claude Code cost and usage history from the metrics log
that ECC's stop:cost-tracker hook writes.
Where the data lives
The tracker appends one JSON object per session-stop to
~/.claude/metrics/costs.jsonl. Each row is a cumulative snapshot for that
session, so to total spend you take the latest row per session_id and
sum across sessions — summing every row multiply-counts.
Row schema:
| Field | Meaning |
|---|---|
timestamp | ISO timestamp of the snapshot |
session_id | Claude Code session identifier |
transcript_path | Path to the session transcript |
model | Model used |
input_tokens / output_tokens | Token counts |
cache_write_tokens / cache_read_tokens | Prompt-cache token counts |
estimated_cost_usd | Precomputed cumulative cost in USD for the session |
Prefer estimated_cost_usd over hand-calculating pricing — model and cache
prices change, and the tracker is the source of truth.
When to Use
- The user asks "how much have I spent?", "what did this session cost?", or "what is my token usage?"
- The user mentions budgets, spending limits, overruns, or cost controls.
- Th…