I Built a Pay-Per-Call API Where the First Call Costs Nothing

#x402 #ai #micropayments #api

AI agents that need a task done should not need an account, an API key, or an
invoice. They should be able to pay cents and get the result.

That is what Hermes Micro-Agent does. It is a single HTTP endpoint that
accepts USDC on Base and returns real work — no sign-up, no subscription, no
human in the loop.

Free services — no payment, no key

Four services are free forever. Call them directly:

# SHA-256 hash of any text
curl -X POST https://92.5.95.177.sslip.io/free/hash \
  -H "Content-Type: application/json" -d '{"prompt":"hello world"}'

# Base64 encode/decode
curl -X POST https://92.5.95.177.sslip.io/free/base64 \
  -H "Content-Type: application/json" -d '{"prompt":"hello"}'

# Unit conversion (length, weight, temperature, data size)
curl -X POST https://92.5.95.177.sslip.io/free/convert \
  -H "Content-Type: application/json" -d '{"prompt":"10 km to miles"}'

# Minify a JSON document
curl -X POST https://92.5.95.177.sslip.io/free/json_minify \
  -H "Content-Type: application/json" -d '{"prompt":"{  \"a\":  1 }"}'

Each returns {"status":"success","task":"...","result":"...","free":true}.

Paid services — $0.10-$0.25 per call

# 1. See the price list
curl https://92.5.95.177.sslip.io/tasks

# 2. Try a task — you get 402 with the address and the price
curl -X POST https://92.5.95.177.sslip.io/task \
  -H "Content-Type: application/json" \
  -d '{"task":"summarize","prompt":"your text here"}'

# 3. Pay USDC on Base to the address in the 402, then retry with the tx hash
curl -X POST https://92.5.95.177.sslip.io/task \
  -H "Content-Type: application/json" \
  -H "X-Payment: 0x<tx_hash>" \
  -d '{"task":"summarize","prompt":"your text here"}'

Or call a service by name — one route per task, so a search for the service
finds the route:

Route	Service	Price
`/summarize`	Summarise text	$0.10
`/extract`	Extract key points	$0.10
`/keywords`	Find keywords	$0.10
`/sentiment`	Detect sentiment	$0.10
`/translate`	Translate	$0.15
`/rewrite`	Rewrite text	$0.15
`/proofread`	Proofread	$0.15
`/code_lint`	Lint Python	$0.15
`/code_explain`	Explain code	$0.15
`/code_refactor`	Refactor code	$0.25
`/code_review`	Review code	$0.25
`/python_debug`	Debug Python	$0.25
`/json_query`	Query JSON	$0.15
`/csv_to_json`	CSV to JSON	$0.15
`/describe_image`	Describe an image	$0.15
`/probe_media`	Probe a media URL	$0.15

Payment

Receiver : 0x078fE079A9440631Bc6AD722D7143dC382b4ea4f
Network  : base (eip155:8453)
Asset    : USDC  0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913

The USDC Transfer is verified on-chain before any work runs. Unpaid or
unverifiable requests get 402 and nothing executes.

Discovery

OpenAPI: https://92.5.95.177.sslip.io/openapi.json
x402 manifest: https://92.5.95.177.sslip.io/.well-known/x402
Listed on x402scan
Source: github.com/Reggiebro/hermes-micro-agent

JSON-RPC utility gateway (free)

# Price one task
curl -X POST https://92.5.95.177.sslip.io/rpc \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"price","params":{"task":"summarize"}}'

# Verify a payment
curl -X POST https://92.5.95.177.sslip.io/rpc \
  -H "Content-Type: application/json" \
  -d '{"jsonrpc":"2.0","id":1,"method":"verify","params":{"tx_hash":"0x...","min_cents":1000}}'

The honest part

The paid tasks are deterministic transformations, not model calls. Same input, same output.
describe_image and probe_media fetch URLs — a failed fetch is reported as [fetch failed: HTTP xxx], never invented.
Unlisted tasks are refused with 400, never faked.
There is no SLA. The endpoint is a single VPS on a free cloud tier.

Why free services at all

A paid-only endpoint is invisible: discovery directories rank by usage, and
usage requires payment, and payment requires being discovered. The four free
services break that loop — an agent can call them with no money and no account,
which is what makes the paid services reachable in the first place.

Try it

curl -X POST https://92.5.95.177.sslip.io/free/hash \
  -H "Content-Type: application/json" -d '{"prompt":"hello world"}'

If you are building an agent and want a deterministic, pay-per-call endpoint
with no account and no subscription — this is it.

DEV Community