Base Gas

Live and historical Base mainnet gas data through x402-protected endpoints, served from https://base-gas-x402-production.up.railway.app.

All values are read directly from the chain. Fees are returned in gwei; transaction costs also come back in ETH and USD.

Setup

See rules/getting-started.md for installation and wallet setup.

Quick Reference

Task	Endpoint	Price	Returns
Current gas	GET /gas	$0.002	Base fee, low/med/high priority tiers, cost estimate in ETH and USD
Compare chains	GET /gas/compare	$0.01	Base, OP, Arbitrum, Ethereum ranked cheapest first, cost in USD
Historical trend	GET /gas/history	$0.01	Time series, min/max/avg/median, cheap-or-expensive verdict
Cheapest hours	GET /gas/cheapest-window	$0.02	Hours to avoid, cheapest hour, savings vs the average hour and in USD
Data coverage	GET /health	free	How much history has been collected so far

See rules/choosing-an-endpoint.md for which route answers which question.

Current Gas

npx agentcash@latest fetch https://base-gas-x402-production.up.railway.app/gas

Parameters:

• gasLimit (optional) - Gas units to price the estimate against. Defaults to 21000.

Price the cost of a Uniswap swap instead of a plain transfer:

npx agentcash@latest fetch "https://base-gas-x402-production.up.railway.app/gas?gasLimit=180000"

Common gas limits:

Operation	gasLimit
ETH transfer	21000
ERC-20 transfer	65000
NFT mint	85000
Uniswap swap	180000
Contract deploy	1500000

Returns: baseFeePerGas, priorityFeePerGas (low/medium/high), gasPrice, estimatedTransferCost (gwei and ETH), blockNumber, fetchedAt.

Compare Chains

npx agentcash@latest fetch https://base-gas-x402-production.up.railway.app/gas/compare

Parameters:

• gasLimit (optional) - Gas units to price each chain against. Defaults to 21000.

Returns: chains ranked cheapest first, cheapest, baseRank, baseVsEthereum (a plain-language multiplier), and unavailable for any chain whose RPC did not respond.

Chains that fail are reported rather than failing the whole request, so a partial comparison still returns useful data.

Historical Trend

npx agentcash@latest fetch "https://base-gas-x402-production.up.railway.app/gas/history?hours=24"

Parameters:

• hours (optional) - Lookback window, 1 to 168. Defaults to 24.

Returns: samples time series, summary (min, max, avg, median), currentGasPrice, verdict, verdictNote, and spreadPercent.

The verdict field is the useful part: cheap, normal, or expensive relative to the requested window, or flat when the window's spread is under 1%. A raw RPC call cannot answer this, because it has no history to compare against.

flat is common on Base and is a real answer: gas is not moving, so there is nothing to wait for. Quote verdictNote rather than reinterpreting it.

Cheapest Hours

npx agentcash@latest fetch "https://base-gas-x402-production.up.railway.app/gas/cheapest-window?hours=168"

Parameters:

• hours (optional) - Lookback window used to compute hourly averages, 1 to 168. Defaults to 168 (7 days).

Returns: hasDailyCycle, a plain-language recommendation, savingsPercent, and hourlyAverages bucketed by hour of day in UTC and ranked cheapest first, plus cheapestHourUtc and priciestHourUtc.

Check hasDailyCycle before using the ranking. When it is false the hours do not meaningfully differ and timing saves nothing; report recommendation instead of naming a cheapest hour.

Check Coverage First (free)

Both history endpoints depend on samples collected over time. Check coverage before paying:

curl -s https://base-gas-x402-production.up.railway.app/health

Returns: under history: samples, hoursCovered, oldestSample, newestSample, sampleIntervalSeconds, retentionHours, durable (whether history survives a redeploy) and lastError. Also nextSteps, ready-to-run commands for the paid routes.

If hoursCovered is smaller than the window you need, the answer will be thin. Every paid response also carries a coverage object so the depth of the underlying data is always visible.

Workflows

Decide whether to transact now

• Check the trend and verdict: GET /gas/history?hours=24
• If verdict is flat, proceed and tell the user there is nothing to wait for
• If cheap, proceed
• If expensive, check whether waiting actually helps: GET /gas/cheapest-window

npx agentcash@latest fetch "https://base-gas-x402-production.up.railway.app/gas/history?hours=24"

Price a specific operation

• Pick the gasLimit for the operation type
• Call /gas with that gasLimit
• Read estimatedTransferCost.usd for the cost in dollars (or .eth)
• If usd is null, the price feed was unavailable: fall back to .eth

npx agentcash@latest fetch "https://base-gas-x402-production.up.railway.app/gas?gasLimit=85000"

Pick the cheapest chain

• (Optional) Check coverage or balance
• Compare chains at the relevant gasLimit
• Route the transaction to cheapest

npx agentcash@latest fetch "https://base-gas-x402-production.up.railway.app/gas/compare?gasLimit=180000"

Schedule a batch job

• Check history coverage: GET /health (free)
• If coverage is at least 24 hours, call /gas/cheapest-window
• If hasDailyCycle is false, report recommendation and run the job whenever
• If true, keep the job out of avoidHoursUtc (worst first)
• Check savingsUsd.vsAverageHour: if the saving is negligible at your volume, run whenever
• Otherwise schedule the job for cheapestHourUtc (convert from UTC)

curl -s https://base-gas-x402-production.up.railway.app/health

npx agentcash@latest fetch "https://base-gas-x402-production.up.railway.app/gas/cheapest-window?hours=168"

Cost Optimization

Use /gas when:

• You only need the current price
• You are pricing a single known operation

Use /gas/history when:

• The question is "is this high or low", not "what is it"
• You need a trend or chart

Use /gas/cheapest-window when:

• The work can wait
• You are scheduling recurring or batch transactions

Efficient patterns

1. Check /health before history calls. It is free and tells you whether the data is deep enough to be worth paying for.
2. One /gas/compare beats four /gas calls. It reads all four chains in a single paid request.
3. Pass gasLimit instead of doing the math. The estimate is returned already priced for the operation you care about, in gwei, ETH and USD.
4. Do not poll. Base blocks are two seconds apart but gas moves slowly; sampling more than once a minute spends money for no new information.

Notes

• Payment settles on Base mainnet (eip155:8453) in USDC via x402.
• Prices are published in the endpoint's OpenAPI document at /openapi.json and are the source of truth if they ever differ from this table.
• The service is open source: github.com/memosr/base-gas-x402.