Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/fuyuxiang/echo-agent/calculatornpx skills add fuyuxiang/echo-agent --skill calculatorgit clone --depth 1 https://github.com/fuyuxiang/echo-agentWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/fuyuxiang/echo-agent/calculator)<a href="https://agentmods.dev/skills/fuyuxiang/echo-agent/calculator"><img src="https://agentmods.dev/badge/skills/fuyuxiang/echo-agent/calculator.svg" alt="Measured on agentmods" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00025 | $0.00645 |
| Opus 5 | $0.00013 | $0.00322 |
| Sonnet 5 | $0.00005 | $0.00129 |
| Haiku 4.5 | $0.00003 | $0.00064 |
Grade C, and why
calculator scanned grade C with 2 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 4d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Downloads and executes remote codehighSupply chain
curl | sh runs whatever the server returns today, which is not necessarily what it returned when this was reviewed.
curl -s "https://open.er-api.com/v6/latest/USD" | python3 -c " Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
curl -s "https://open.er-api.com/v6/latest/USD" | python3 -c " What it actually says
Calculator
Math, units, dates, and currency conversion.
Math Expressions
Safe evaluation via Python:
import ast
result = eval(compile(ast.parse("2**10 + 3.14 * 2", mode='eval'), '', 'eval'))
Complex math:
import math
math.sqrt(144) # 12.0
math.log2(1024) # 10.0
math.factorial(10) # 3628800
math.pi # 3.14159...
Unit Conversions
| Category | Conversions |
|---|---|
| Temperature | C↔F: F = C*9/5+32 |
| Length | km↔mi (×0.621371), m↔ft (×3.28084), cm↔in (×0.393701) |
| Weight | kg↔lb (×2.20462), g↔oz (×0.035274) |
| Volume | L↔gal (×0.264172) |
| Data | KB↔MB↔GB↔TB (÷1024) |
Date Calculations
from datetime import datetime, timedelta
from zoneinfo import ZoneInfo
# Days between dates
(datetime(2026, 12, 31) - datetime.now()).days
# Add/subtract time
datetime.now() + timedelta(days=30, hours=2)
# Timezone conversion
dt = datetime.now(ZoneInfo("Asia/Shanghai"))
dt.astimezone(ZoneInfo("America/New_York"))
Currency Exchange
Free API (no key required):
curl -s "https://open.er-api.com/v6/latest/USD" | python3 -c "
import sys,json; d=json.load(sys.stdin)['rates']
print(f\"1 USD = {d['CNY']:.4f} CNY\")
print(f\"1 USD = {d['EUR']:.4f} EUR\")
print(f\"1 USD = {d['JPY']:.2f} JPY\")
"
Common Formulas
# BMI
bmi = weight_kg / (height_m ** 2)
# Compound interest
A = P * (1 + r/n) ** (n*t)
# Percentage change
change = (new - old) / old * 100
Script
python3 scripts/calc.py eval "2**32 - 1"
python3 scripts/calc.py convert 100 km mi
python3 scripts/calc.py date "2026-12-31" days-until
python3 scripts/calc.py currency 100 USD CNY
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 4d ago First seen · 92 lines · 25 tokens per session scan C a5e5a044c657
calculator is a skill published in the GitHub repository fuyuxiang/echo-agent (988 stars, last pushed 4d ago), licensed MIT. It adds 25 tokens to every session and 645 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it C with 2 findings (downloads and executes remote code, makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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