0xProject · pgrzesik · Jun 24, 2026 · Jun 24, 2026
diff --git a/Cargo.lock b/Cargo.lock
diff --git a/Cargo.toml b/Cargo.toml
@@ -91,6 +91,18 @@ keyring = { version = "3", features = [
     "crypto-rust",
     "async-io",
 ] }
+x402-reqwest = { version = "2.0.1", default-features = false, features = ["json"] }
+mpp = { version = "0.10.4", default-features = false, features = ["client", "tempo", "middleware", "reqwest-rustls-tls"] }
+# `telemetry` pulls `tracing` (the v2_eip155_upto client references it
+# unconditionally, so `client` alone won't compile). The CLI already uses tracing.
+x402-chain-eip155 = { version = "2.0.1", features = ["client", "telemetry"] }
+alloy-signer-local = "2"
+x402-types = { version = "2.0.1", default-features = false }
+# The payment crates (x402-reqwest, mpp) are built on reqwest 0.13, while the
+# keyed API client (src/api) stays on 0.12. Alias the 0.13 line under a second
+# name so the payment adapters speak the same reqwest types those crates expose
+# without forcing a crate-wide HTTP upgrade.
+reqwest_payments = { package = "reqwest", version = "0.13", default-features = false, features = ["rustls", "query"] }
 
 [dev-dependencies]
 assert_cmd = "2"

diff --git a/README.md b/README.md
@@ -7,8 +7,8 @@ Trade tokens across Solana and EVM chains from your terminal. Built for both hum
 ## Quick Start
 
 ```bash
-# Build from source
-cargo install --path .
+# Install (macOS / Linux) — see Installation below for Windows / from source
+curl -fsSL https://raw.githubusercontent.com/0xProject/0x-cli/main/scripts/install.sh | sh
 
 # Configure
 0x config init
@@ -27,6 +27,7 @@ cargo install --path .
 - **4 APIs**: EVM Swap (Allowance Holder), Gasless Swap, Solana Swap, Cross-Chain
 - **21 chains**: Ethereum, Base, Arbitrum, Optimism, Polygon, BSC, Avalanche, Linea, Scroll, Blast, Mantle, Berachain, Sonic, Unichain, World Chain, Abstract, Ink, Monad, HyperEVM, Solana, Tron
 - **Agent-first**: Auto-detect non-TTY for JSON output, structured error codes, stable exit codes, inline `RESPONSE:` schemas in every `--help`
+- **Pay-per-request (no API key)**: `--pay x402-evm` or `--pay mpp` settles ~$0.01 USDC per request via the 0x agent gateway — for autonomous agents with a funded wallet
 - **Safe by default**: OS keyring for wallet secrets, transaction simulation before every execution, `--dry-run` mode, exact token approvals
 - **Rich UX**: Colored tables, progress spinners, interactive confirmation, shell completions
 
@@ -46,10 +47,10 @@ Pin a specific version or change the install directory:
 
 ```bash
 # Install a specific version
-curl -fsSL https://raw.githubusercontent.com/0xProject/0x-cli/main/scripts/install.sh | ZEROX_VERSION=v0.1.0 sh
+curl -fsSL https://raw.githubusercontent.com/0xProject/0x-cli/main/scripts/install.sh | ZEROEX_VERSION=v0.1.0 sh
 
 # Install somewhere on your PATH
-curl -fsSL https://raw.githubusercontent.com/0xProject/0x-cli/main/scripts/install.sh | ZEROX_BIN_DIR=/usr/local/bin sh
+curl -fsSL https://raw.githubusercontent.com/0xProject/0x-cli/main/scripts/install.sh | ZEROEX_BIN_DIR=/usr/local/bin sh
 ```
 
 On **Windows**, download the `.zip` for `x86_64-pc-windows-msvc` from the
@@ -119,10 +120,10 @@ By default, `wallet.evm` and `wallet.solana` (when given key material rather tha
 | `0x config set wallet.evm <key> --plaintext` | `~/.0x-config/config.toml` |
 | `0x config set wallet.solana /path/to/file.json` | `~/.0x-config/config.toml` (it's a path) |
 | `0x config set wallet.solana <base58>` | OS keyring |
-| `ZEROX_EVM_PRIVATE_KEY` / `ZEROX_SOLANA_KEYPAIR` env var | Read directly, never persisted |
+| `ZEROEX_EVM_PRIVATE_KEY` / `ZEROEX_SOLANA_KEYPAIR` env var | Read directly, never persisted |
 | `0x config set wallet.tron <hex-key>` | OS keyring |
 | `0x config set wallet.tron <hex-key> --plaintext` | `~/.0x-config/config.toml` |
-| `ZEROX_TRON_PRIVATE_KEY` env var | Read directly, never persisted |
+| `ZEROEX_TRON_PRIVATE_KEY` env var | Read directly, never persisted |
 
 `0x config show` reports keyring-stored wallets as `<stored in keyring>`. If the OS keyring is unavailable (e.g. headless Linux with no DBus), use `--plaintext` or the env vars.
 
@@ -132,13 +133,13 @@ Environment variables always take precedence over config file values.
 
 | Variable | Description |
 |----------|-------------|
-| `ZEROX_API_KEY` | 0x API key |
-| `ZEROX_EVM_PRIVATE_KEY` | EVM private key (hex) |
-| `ZEROX_SOLANA_KEYPAIR` | Solana keypair file path or base58 |
-| `ZEROX_TRON_PRIVATE_KEY` | Tron private key (hex) |
-| `ZEROX_DEFAULT_CHAIN` | Default chain name or ID |
-| `ZEROX_RPC_URL` | Override RPC URL for any chain |
-| `ZEROX_TELEMETRY` | Set falsy (`0`/`false`/`off`) to disable usage telemetry |
+| `ZEROEX_API_KEY` | 0x API key |
+| `ZEROEX_EVM_PRIVATE_KEY` | EVM private key (hex) |
+| `ZEROEX_SOLANA_KEYPAIR` | Solana keypair file path or base58 |
+| `ZEROEX_TRON_PRIVATE_KEY` | Tron private key (hex) |
+| `ZEROEX_DEFAULT_CHAIN` | Default chain name or ID |
+| `ZEROEX_RPC_URL` | Override RPC URL for any chain |
+| `ZEROEX_TELEMETRY` | Set falsy (`0`/`false`/`off`) to disable usage telemetry |
 | `DO_NOT_TRACK` | Set to `1` to disable usage telemetry |
 | `NO_COLOR` | Disable colored output |
 
@@ -277,6 +278,42 @@ Nothing to configure — the keypair lives in memory only.
 0x status 0xdef456... --type cross-chain --chain base --poll --poll-interval 10
 ```
 
+### Pay per request (x402 / MPP)
+
+Instead of a `0x-api-key`, `price` and `swap` can pay **~$0.01 USDC per request**
+through the 0x agent gateway — useful for an autonomous agent with a funded wallet
+and no key. Add `--pay` with one of two payment rails:
+
+| `--pay` | Rail | Wallet needs |
+|---------|------|--------------|
+| `x402-evm` | [x402](https://www.x402.org) over Base — signs an EIP-3009 USDC authorization (off-chain, no gas) | USDC on Base |
+| `mpp` | [MPP](https://mpp.dev) over Tempo (chainId 4217) — broadcasts a USDC.e transfer | USDC.e **and** native gas on Tempo |
+
+```bash
+# Pay for a price check with x402 (EVM wallet signs; no API key needed)
+0x price --chain base --sell 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 \
+  --buy 0x4200000000000000000000000000000000000006 --amount 1000000 \
+  --pay x402-evm --max-payment 0.05
+
+# Pay for a swap quote via MPP/Tempo, then execute on-chain as usual
+0x swap --chain base --sell 0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913 \
+  --buy 0x4200000000000000000000000000000000000006 --amount 1000000 \
+  --pay mpp --yes
+```
+
+- **EVM AllowanceHolder only.** Rejected (free, `INPUT_INVALID`) with `--gasless`,
+  Solana/Tron, or `--buy-amount` (exact-out).
+- **`--max-payment <USD>`** (default `0.05`) caps the spend. If the gateway asks for
+  more, the CLI refuses **before signing/broadcasting** — `PAYMENT_EXCEEDS_LIMIT`
+  (exit 41), nothing spent.
+- **The payment is real, non-refundable money** charged per request — including when
+  a later on-chain swap reverts. Don't poll `price --pay` in a loop. The settlement
+  (tx hash, payer, amount) is reported under `metadata.payment` in JSON output.
+- `swap --pay` pays only for the **quote**; the on-chain swap still uses your wallet
+  and RPC. See exit codes 40–44 and the `PAYMENT_*` rows under [Error Codes](#error-codes).
+- For `--pay mpp`, point the Tempo RPC wherever you like with `--tempo-rpc <url>` or
+  `0x config set rpc.tempo <url>` (defaults to `https://rpc.tempo.xyz`).
+
 ## AI Agent Integration
 
 The CLI is designed as a first-class tool for AI agents and scripts.
@@ -350,7 +387,7 @@ On error:
     "message": "No API key configured",
     "category": "config",
     "retryable": false,
-    "suggestion": "Run '0x config set api_key <your-key>' or set ZEROX_API_KEY env var"
+    "suggestion": "Run '0x config set api_key <your-key>' or set ZEROEX_API_KEY env var"
   }
 }
 ```
@@ -458,7 +495,7 @@ Every interactive prompt has a flag equivalent:
 - **Redaction**: `0x config show` and `0x config get` never reveal secret material. Wallets stored in the keyring show as `<stored in keyring>`; plaintext wallets show as `***redacted***`; Solana file paths show verbatim because the path itself isn't sensitive.
 - **Transaction simulation**: EVM and Solana transactions are simulated via `eth_call` or `simulate_transaction` before submission. Tron cross-chain transactions are not pre-simulated.
 - **Approval strategy**: Default is `exact` (only approve the needed amount). Use `--approval unlimited` for max approval.
-- **Environment variables**: Sensitive values like private keys can be set via env vars (`ZEROX_EVM_PRIVATE_KEY`, `ZEROX_SOLANA_KEYPAIR`) to avoid persisting them at all — read-once, never written to disk or keyring.
+- **Environment variables**: Sensitive values like private keys can be set via env vars (`ZEROEX_EVM_PRIVATE_KEY`, `ZEROEX_SOLANA_KEYPAIR`) to avoid persisting them at all — read-once, never written to disk or keyring.
 
 ## Telemetry
 
@@ -485,7 +522,7 @@ The CLI sends **anonymous, opt-out** usage statistics (via Amplitude) to help us
 
 ```bash
 0x config set telemetry.enabled false   # persistent
-export ZEROX_TELEMETRY=0                 # per-shell
+export ZEROEX_TELEMETRY=0                 # per-shell
 export DO_NOT_TRACK=1                    # cross-tool standard
 ```
 

diff --git a/scripts/install.sh b/scripts/install.sh
@@ -7,13 +7,13 @@
 # checksum, and installs it to a bin directory on your PATH.
 #
 # Knobs (all optional, set as environment variables):
-#   ZEROX_VERSION   version to install, e.g. v0.1.0   (default: latest release)
-#   ZEROX_BIN_DIR   install directory                 (default: ~/.local/bin)
+#   ZEROEX_VERSION   version to install, e.g. v0.1.0   (default: latest release)
+#   ZEROEX_BIN_DIR   install directory                 (default: ~/.local/bin)
 #
 # Examples:
 #   curl -fsSL .../install.sh | sh
-#   curl -fsSL .../install.sh | ZEROX_VERSION=v0.1.0 sh
-#   curl -fsSL .../install.sh | ZEROX_BIN_DIR=/usr/local/bin sh
+#   curl -fsSL .../install.sh | ZEROEX_VERSION=v0.1.0 sh
+#   curl -fsSL .../install.sh | ZEROEX_BIN_DIR=/usr/local/bin sh
 
 set -eu
 
@@ -82,7 +82,7 @@ esac
 target="${cpu}-${os_name}"
 
 # --- resolve version --------------------------------------------------------
-version="${ZEROX_VERSION:-}"
+version="${ZEROEX_VERSION:-}"
 if [ -z "$version" ]; then
   info "${DIM}Resolving latest release...${RESET}"
   # The /releases/latest page 302-redirects to /releases/tag/<version>; parse
@@ -96,7 +96,7 @@ if [ -z "$version" ]; then
       | awk '/^[[:space:]]*Location:/ {print $2}' | tail -n1)"
   fi
   version="${loc##*/}"
-  [ -n "$version" ] || err "could not determine the latest version; set ZEROX_VERSION=vX.Y.Z"
+  [ -n "$version" ] || err "could not determine the latest version; set ZEROEX_VERSION=vX.Y.Z"
 fi
 case "$version" in v*) ;; *) version="v$version" ;; esac
 
@@ -148,11 +148,11 @@ binpath="$tmp/${BIN}-${target}/${BIN}"
 chmod +x "$binpath"
 
 # --- choose install dir -----------------------------------------------------
-bin_dir="${ZEROX_BIN_DIR:-$HOME/.local/bin}"
+bin_dir="${ZEROEX_BIN_DIR:-$HOME/.local/bin}"
 mkdir -p "$bin_dir" 2>/dev/null || err "cannot create install dir: $bin_dir"
 if [ ! -w "$bin_dir" ]; then
   err "install dir is not writable: $bin_dir
-Re-run with a writable dir, e.g.  ZEROX_BIN_DIR=\$HOME/.local/bin
+Re-run with a writable dir, e.g.  ZEROEX_BIN_DIR=\$HOME/.local/bin
 or with elevated permissions for a system path."
 fi
 

diff --git a/skills/0x-trade/SKILL.md b/skills/0x-trade/SKILL.md
@@ -101,11 +101,29 @@ On error, `status` is `"error"` and a structured `error` object replaces `data`:
 | 11 | Transaction reverted on-chain | Don't retry as-is; explain to the user. |
 | 12 | Pending / timed out — tx may still land | Poll with `0x status` (see references). |
 | 20 | User declined the confirmation prompt | Stop; don't re-run. |
+| 40 | Agent-payment challenge invalid (`--pay`) — no payable scheme offered | Nothing spent; report it. |
+| 41 | Payment exceeded `--max-payment` — refused before signing | **Nothing spent.** Only raise the cap if the amount is expected. |
+| 42 | Payment signing failed | Verify the payment wallet; nothing spent. |
+| 43 | Payment settlement failed | **Money may have been spent** with no usable result — don't blindly retry; check the wallet. |
+| 44 | Payment wallet unfunded (USDC/USDC.e or native gas) | Fund the payment wallet. |
 | 25 | Preview emitted, confirmation required (`--yes` missing) | Show the quote to the user, or re-run with `--yes`. |
 | 30 | Dry-run completed | Report the simulated result. |
 
 The full error-code catalog (code → category → retryable → action) is in `references/errors.md`.
 
+## Paying per request instead of an API key (`--pay`)
+
+`price` and `swap` accept `--pay <x402-evm|mpp>` to pay ~$0.01 in USDC per request through the 0x agent gateway instead of using an API key — useful for an autonomous agent with a funded wallet and no key.
+
+- **EVM AllowanceHolder only.** Rejected (`INPUT_INVALID`) with `--gasless`, Solana, or Tron.
+- **`x402-evm`**: signs an EIP-3009 USDC authorization on Base; needs USDC in the EVM wallet.
+- **`mpp`**: broadcasts a USDC.e transfer on Tempo (chainId 4217); needs USDC.e **and** native gas there. Override the RPC with `--tempo-rpc` / `ZEROEX_TEMPO_RPC_URL`.
+- **`--max-payment <USD>`** (default `0.05`) caps the spend; the CLI refuses *before* signing/broadcasting if the gateway asks for more (`PAYMENT_EXCEEDS_LIMIT`, exit 41 — nothing spent).
+- **Every paid request costs real, non-refundable money**, including when the on-chain swap later reverts. Don't poll `price --pay` in a loop. The settlement (tx hash, payer, amount) is in `metadata.payment`.
+- `swap --pay` pays only for the *quote*; the on-chain swap still uses your wallet + RPC as usual.
+
+See the `PAYMENT_*` rows in `references/errors.md` (exit 40–44) for recovery — exit 41 means nothing was spent; exit 43 means money may have moved without a usable result.
+
 ## Going deeper — read on demand
 
 Read the matching reference only when the task needs it:

diff --git a/skills/0x-trade/references/config.md b/skills/0x-trade/references/config.md
@@ -45,15 +45,15 @@ Non-interactive (agent-driven) setup:
 
 | Var | Overrides |
 |-----|-----------|
-| `ZEROX_API_KEY` | `api_key` |
-| `ZEROX_EVM_PRIVATE_KEY` | `wallet.evm` |
-| `ZEROX_SOLANA_KEYPAIR` | `wallet.solana` (path or base58) |
-| `ZEROX_TRON_PRIVATE_KEY` | `wallet.tron` |
-| `ZEROX_DEFAULT_CHAIN` | `defaults.chain` |
-| `ZEROX_RPC_URL` | RPC for the current command |
-| `ZEROX_OUTPUT` | `-o/--output` format |
-| `ZEROX_PROFILE` | Config profile to use (overrides active_profile) |
-| `ZEROX_TELEMETRY` | Set falsy (`0`/`false`/`off`) to disable usage telemetry |
+| `ZEROEX_API_KEY` | `api_key` |
+| `ZEROEX_EVM_PRIVATE_KEY` | `wallet.evm` |
+| `ZEROEX_SOLANA_KEYPAIR` | `wallet.solana` (path or base58) |
+| `ZEROEX_TRON_PRIVATE_KEY` | `wallet.tron` |
+| `ZEROEX_DEFAULT_CHAIN` | `defaults.chain` |
+| `ZEROEX_RPC_URL` | RPC for the current command |
+| `ZEROEX_OUTPUT` | `-o/--output` format |
+| `ZEROEX_PROFILE` | Config profile to use (overrides active_profile) |
+| `ZEROEX_TELEMETRY` | Set falsy (`0`/`false`/`off`) to disable usage telemetry |
 | `DO_NOT_TRACK` | Set to `1` to disable usage telemetry (cross-tool standard) |
 | `NO_COLOR` | Disables colored output |
 
@@ -78,14 +78,14 @@ section.
 ```
 
 When a profile is active, every API command prints `Profile '<name>' → <url>` on
-stderr. The banner is suppressed by --quiet. `ZEROX_PROFILE` selects a profile per-environment; `--api-key` /
-`ZEROX_API_KEY` still beat the profile's key.
+stderr. The banner is suppressed by --quiet. `ZEROEX_PROFILE` selects a profile per-environment; `--api-key` /
+`ZEROEX_API_KEY` still beat the profile's key.
 
 ## Telemetry
 
 The CLI sends anonymous usage stats (which command ran, exit code, duration, chain name, CLI version, OS) to help prioritize work. It is **opt-out** and deliberately minimal:
 
 - **Never sent:** token addresses, amounts, transaction/trade hashes, wallet addresses, API keys, RPC URLs, error messages, or IP.
 - **Identifier:** a random `telemetry.install_id` (a UUID, not a device/hardware fingerprint), shown in `config show`.
-- **Opt out** any of three ways: `0x config set telemetry.enabled false`, `ZEROX_TELEMETRY=0`, or `DO_NOT_TRACK=1`.
+- **Opt out** any of three ways: `0x config set telemetry.enabled false`, `ZEROEX_TELEMETRY=0`, or `DO_NOT_TRACK=1`.
 - Events spool to `~/.0x-config/telemetry-queue.jsonl` and flush in the background, so they never add latency to a command.
diff --git a/skills/0x-trade/references/cross-chain.md b/skills/0x-trade/references/cross-chain.md
@@ -2,7 +2,7 @@
 
 Swap a token on one chain for a token on another in a single command. Supports EVM↔EVM, EVM↔Solana, and EVM↔Tron. The CLI fetches multiple bridge quotes, executes the origin-chain transaction, and can track the bridge until funds land on the destination.
 
-**Tron:** Tron addresses are base58check (`T…`). A Tron wallet (`wallet.tron` / `ZEROX_TRON_PRIVATE_KEY`) is required to bridge from or to Tron. Tron is bridging-only — it is not available in `swap`, `price`, or `gasless`.
+**Tron:** Tron addresses are base58check (`T…`). A Tron wallet (`wallet.tron` / `ZEROEX_TRON_PRIVATE_KEY`) is required to bridge from or to Tron. Tron is bridging-only — it is not available in `swap`, `price`, or `gasless`.
 
 ## Quote + execute
 

diff --git a/skills/0x-trade/references/errors.md b/skills/0x-trade/references/errors.md
@@ -8,7 +8,7 @@ Every error carries: `code` (stable), `category`, `retryable`, `message`, and us
 |--------------|----------|-----:|:---------:|----------|
 | `CONFIG_NOT_FOUND` | config | 3 | no | Run `0x config init`. |
 | `CONFIG_INVALID` | config | 3 | no | Inspect `~/.0x-config/config.toml`; fix or re-init. |
-| `API_KEY_MISSING` | config | 5 | no | `0x config set api_key <key>` or `ZEROX_API_KEY`. |
+| `API_KEY_MISSING` | config | 5 | no | `0x config set api_key <key>` or `ZEROEX_API_KEY`. |
 | `WALLET_NOT_FOUND` | config | 3 | no | `0x config set wallet.evm <key>` / `wallet.solana <path>`. |
 | `WALLET_INVALID` | config | 3 | no | The stored key/keypair doesn't parse — re-set it. |
 | `KEYRING_UNAVAILABLE` | config | 3 | no | No OS keyring (headless Linux) — re-set the secret with `--plaintext` or use env vars. |
@@ -32,6 +32,11 @@ Every error carries: `code` (stable), `category`, `retryable`, `message`, and us
 | `BRIDGE_FAILED` | bridge | 1 | no | Check `data.failure_reason` via `0x status`. |
 | `BRIDGE_TIMEOUT` | bridge | 12 | yes | Bridge in flight — keep polling `0x status --type cross-chain`. |
 | `USER_CANCELLED` | input | 20 | no | The user said no. Stop. |
+| `PAYMENT_CHALLENGE_INVALID` | payment | 40 | no | The agent gateway's 402 offered no scheme the CLI can pay (`--pay`). Nothing spent — report it. |
+| `PAYMENT_EXCEEDS_LIMIT` | payment | 41 | no | Required payment exceeded `--max-payment`; the CLI refused to sign. **Nothing spent.** Raise the cap only if the amount is expected. |
+| `PAYMENT_SIGNING_FAILED` | payment | 42 | no | Signing the x402 payment authorization failed — verify the configured payment wallet. Nothing spent. |
+| `PAYMENT_SETTLEMENT_FAILED` | payment | 43 | no | Payment submitted but rejected/failed on settlement. **Money may have been spent** without a usable response — do not blindly retry; check the wallet. |
+| `PAYMENT_WALLET_UNFUNDED` | payment | 44 | no | Payment wallet lacks USDC/USDC.e (or native gas for an MPP push). Fund it. |
 
 ## SIMULATION_FAILED (exit 10) — the special case
 

diff --git a/skills/0x-trade/references/solana.md b/skills/0x-trade/references/solana.md
@@ -24,7 +24,7 @@ Read-only — no keypair needed, no keychain prompt.
   --yes -o json-envelope
 ```
 
-Requires a Solana keypair: `0x config set wallet.solana <path-or-base58>` or `ZEROX_SOLANA_KEYPAIR`. The transaction is simulated before submission; simulation failures exit 10 with the first simulation logs in `error.details.simulation_logs`.
+Requires a Solana keypair: `0x config set wallet.solana <path-or-base58>` or `ZEROEX_SOLANA_KEYPAIR`. The transaction is simulated before submission; simulation failures exit 10 with the first simulation logs in `error.details.simulation_logs`.
 
 ## Flag differences vs EVM (important)