agentic-payments

Agentic Payments

Pay HTTP 402-protected resources on the user's behalf. InFlow speaks two payment protocols - MPP and x402 - but the flow is the same for both: shared setup (install, run, authenticate), then a router that picks the protocol from the seller's 402 header, then one Paying a 402 resource section that covers both. A per-protocol delta table at the top of that section lists the handful of real differences (header name, credential name, filters, error codes); read your row, then follow the shared steps.

Installing

Install the signed native CLI through one of these channels:

Current install instructions live at https://inflowcli.ai/.

Running

InFlow runs as a standalone CLI or an MCP server.

MCP: add an inflow server to your MCP client config that runs inflow --mcp.

MCP mode exposes every CLI command as a tool. Call tools/list on the MCP server for the authoritative inventory; arguments mirror the CLI flags one-to-one.

Common commands / options

The CLI is the source of truth for exact flags, enums, and output shapes - run inflow <command> --schema for one command, or inflow --llms-full for everything. This playbook covers when and why, not exhaustive parameter lists; when you need a precise flag name, value set, or response shape, query the CLI rather than guessing.

• inflow --llms (or --llms-full for parameter detail) - discover all commands. inflow <command> --schema for a single command's JSON Schema.
• inflow --skill - print this playbook (no frontmatter) to stdout. Use it to paste into the system-prompt field of an MCP host that doesn't natively load skills: inflow --skill | pbcopy.
• Default output is toon. Override with --format <fmt>; for programmatic parsing prefer json (single document) or jsonl (line-delimited).
• Multi-step flows return _next.command - run it to continue.
• --auth <path> identifies a legacy plaintext credential file for deletion; it is not a credential backend.
• --api-key <key> or INFLOW_API_KEY=<key> is an alternative to device-flow auth.

Authenticate

Authentication is shared by both protocols - do it once, before either payment flow. Don't start a payment until the user is authenticated.

Credential-bearing commands require the encrypted local vault. If the CLI reports that the vault is uninitialized or locked, tell the user to run inflow vault unlock themselves in a terminal, then retry. Never ask for or accept the vault PIN or passphrase through chat, an MCP tool, a command-line flag, or an environment variable.

Check the current state first - the user may already be logged in:

inflow auth status

A successful auth status returns authenticated: true plus auth_method (device_token or api_key), a truncated access_token preview (never the full token), credentials_path, connection, and possibly an update field. Run the command to see the full shape.

If the response includes an update field, a newer version of inflow is published.

Surface and defer. Tell the user a newer version is available and share the install instructions at https://inflowcli.ai/. Then proceed with the current version. Only block on the upgrade if a subsequent command fails with VERSION_UNSUPPORTED (or an HTTP 426 from the API), at which point the upgrade is mandatory and you should not retry until it lands.

If authenticated is false, start the device flow:

inflow auth login --client-name "<your-agent-name>"

Replace <your-agent-name> with the name of your agent or application (for example "Personal Assistant", "Shopping Bot"). The device-authorization page in the user's browser displays this name when they approve the connection. Use a clear, unique, identifiable name.

The response includes a verification_url (present this to the user), a phrase, and a _next.command. Run that command immediately to poll until authenticated. Do not wait for the user to respond before starting the poll.

If your environment can't relay the verification phrase to the user while a separate polling command blocks I/O, use inline polling instead:

inflow auth login --client-name "<name>" --interval 5 --timeout 300

API key alternative: if the user provides an API key, set INFLOW_API_KEY=<key> in the environment (or pass --api-key <key> to any command) instead of running auth login. The API key takes precedence over a saved device token.

If auth status returns VAULT_LOCKED, authentication status is unavailable rather than unauthenticated. Tell the user to run inflow vault unlock themselves in a terminal, then retry auth status.

Which protocol? - start here

Before paying, decide which protocol the resource uses. You do not choose it - the seller's 402 challenge decides. Run one read-only, no-auth command and let it detect both:

inflow inspect <url>

inflow inspect probes the URL once and decodes both MPP and x402 challenges from the same 402. Read its detected array to pick the protocol. For MPP, also read each challenge's intent: use mpp subscribe for subscription and mpp pay for one-time charge.

If detected includes aep and also reveals a payment protocol, continue with the matching mpp pay or x402 pay; the payment commands perform AEP authentication before creating the payment transaction. If aep.blocked is true, AEP authentication is required before payment terms can be inspected; use inflow aep fetch <url> for access-only requests or ask whether to authenticate before attempting payment.

If inspect returns outcome: "no-payment-required", the URL isn't paywalled - there's nothing to pay.

Paying a 402 resource

This section covers one-time MPP charges and x402 payments. MPP subscriptions use Subscribing to an MPP resource. Prerequisite: you are authenticated (see Authenticate). First find your protocol's row in the Protocol deltas table below - it names the 402 header that selected it, the matching model, the filter flags, and the Fetch command that completes the seller request. Everything else in this section applies to both protocols.

Sequencing. Run pre-flight before pay - pay fails or double-charges if the pre-flight checks didn't clear. inspect and decode are read-only and need no auth, so they may run before you authenticate if useful (e.g. sizing up a paywall first). If the seller requires AEP before payment, pay authenticates with the Service first, then creates the payment only after the legitimate 402 is available. Do not run a separate aep grant just to continue payment.

Protocol deltas

Throughout this section <mpp|x402> means "use your protocol's prefix." For the exact parameters and output shape of any command below, run inflow <command> --schema.

Step 1: Pre-flight evaluation

# 1. Parse what the seller will accept - read-only, no auth (both protocols in one probe)
inflow inspect <url>

# (Already have the raw 402 header from a prior response? Decode it directly instead of re-probing:)
inflow <mpp|x402> decode '<402 header value>'

# 2. List what the buyer's account can pay with (use the protocol from `detected`)
inflow <mpp|x402> supported

# 3. Check balances for the candidate currency/asset(s)
inflow balances list

inflow inspect returns what the seller accepts under its mpp and x402 keys - the price is each challenge's amount field (raw atomic units for x402; the asset is the on-chain contract address, not a symbol). decode parses a single raw header you already hold (and also accepts a base64url credential / receipt). supported returns what the account can pay with; balances list returns available per currency. Run the commands to see the exact shapes.

Decide whether you can pay (apply your protocol's matching model from the delta table):

Optional filters narrow which offer to fulfil - optional, AND-combined, applied on pay, and an empty result fails with NO_FILTERED_MATCH (it does not fall through to a default order). One non-obvious case: MPP's --instrument-id picks how to fund (an instrument-rail / fiat challenge), not which challenge. For the exact filter flags and accepted values per protocol, run inflow <mpp|x402> pay --schema.

Decimal precision. balances.available and the challenge/amount value are decimal strings preserving BigDecimal precision. Never parse them to a JS Number - that drops precision. Compare as strings, or use a BigInt / decimal.js-style library.

Step 2: Pay

Before initiating the call, summarize the intent to the user in chat: amount, currency, resource URL, and the method/rail (MPP) or scheme/network (x402). The user verifies the canonical details on the approval screen; the chat summary is what they read first. Example:

"I'm about to pay 0.10 USDC to api.foo.dev for /dataset.csv. Requesting approval next."

Fast path (recommended). When the agent can block until the payment finishes, set --interval N and let the CLI run the whole flow in one call - probe, decode, prepare, await approval, replay against the seller, return the body:

inflow <mpp|x402> pay <url> --interval 5 --max-attempts 180

The result includes outcome, transaction_id, response_status, settled, the seller body inline (or output_saved_to if --output-file is set), and the now-consumed credential (credential for MPP, encoded_payload for x402). On the fast path the CLI has already replayed that credential to fetch the body - it appears in the result for reference only; do not replay it yourself. To surface approval_url before the call returns, add --format jsonl - frames stream line-by-line. With the default json (or toon), the agent only sees the final buffered result.

outcome values. A completed pay returns one of three terminal outcomes - branch on it, don't assume paid:

Two-step path. Use this when the agent's host can't block I/O long enough for the user to approve (chat UIs that yield between turns). Drop --interval; the first call returns transaction_id + approval_id + approval_url + a _next Fetch command/tool input. Fetch owns polling and seller replay.

inflow <mpp|x402> pay <url>
# -> { "transaction_id": "txn_abc", "approval_id": "appr_xyz", "approval_url": "https://app.inflowpay.ai/approvals/appr_xyz", "_next": { "command": "<mpp|x402> fetch txn_abc <url> --interval 5 --max-attempts 180", "tool": "<mpp|x402>_fetch", "input": { "transactionId": "txn_abc", "resourceUrl": "<url>" } } }

Mind the two distinct ids: poll, replay, and resume all use transaction_id; cancel uses approval_id (inflow <mpp|x402> cancel <approval_id>). Both are returned by pay.

For non-GET requests, pass --method, --data, --header (repeatable):

inflow <mpp|x402> pay https://seller.example.com/api/widgets --method POST --data '{"sku":"widget-1"}' --header "X-Custom: value" --interval 5 --max-attempts 180

Idempotency (x402 only). Set --payment-id <id> whenever a retry on transport failure is possible - the server treats two requests with the same id as the same logical payment, so a retry after a network blip won't double-charge. Use a stable random opaque value generated once per intent; reuse the same id on transport retry; regenerate only when the user explicitly wants a fresh charge. Don't tie the id to wall-clock time - a date-based id silently double-charges on next-day "buy this again" requests. Without --payment-id, the server generates one each call - fine for one-shots, unsafe for retries. (Format constraints: inflow x402 pay --schema.)

inflow x402 pay <url> --payment-id "<stable-opaque-id>"

Sensitive / binary output. Fetch never exposes the one-time bearer credential (credential for MPP, encoded_payload for x402). For the seller's response body, --output-file <path> writes bytes to disk and replaces body / body_base64 with output_saved_to: <path> - pair with --no-show-body for binary content (PDFs, images, audio, datasets) so bytes never appear inline as base64:

inflow <mpp|x402> pay https://api.foo.dev/dataset.csv --interval 5 --max-attempts 180 --output-file /tmp/dataset.csv --no-show-body

Polling discipline. Persist transaction_id as soon as pay returns it. Then:

• Run _next.command, or call _next.tool with _next.input, immediately. Don't wait for the user to confirm before polling starts.
• If polling is interrupted - network drop, session bounce, user kills the agent - resume with inflow <mpp|x402> fetch <transaction_id> <url> --interval 5 --max-attempts 180. Only create a new transaction if the original expired (PAYMENT_EXPIRED for MPP, APPROVAL_TIMEOUT for x402), was denied/cancelled, or its credential is already consumed.
• If POLLING_TIMEOUT fires before approval, ask the user whether to keep waiting or cancel - don't silently restart the poll.
• If >12 minutes elapsed without a user response (≈3 min before the 15-minute approval window closes), surface that explicitly so they can act before the window closes.
• If the user aborts ("nevermind", "cancel that"), call inflow <mpp|x402> cancel <approval_id> before exiting. Otherwise the approval sits pending for 15 minutes and triggers phantom notifications in the user's InFlow app.

Fetch sends a ready payment credential to the seller at most once per invocation. If Fetch returns PAYMENT_REPLAY_OUTCOME_UNKNOWN, tell the user the seller might have received or consumed the credential and do not automatically replay it.

When AEP is required, Fetch still sends the payment credential at most once. The final seller request carries both credentials without exposing either one in JSON output, logs, cache keys, or chat.

Limits

Worked example (MPP)

A user asks the agent to fetch a paywalled dataset at https://api.foo.dev/dataset.csv.

Pre-flight: inflow inspect <url> reports detected: ["mpp"] with the seller's challenges; then inflow mpp supported (methods the buyer can pay with) and inflow balances list. The seller offers the inflow method in USDC; the user's 100.5 USDC balance covers the 0.10 USDC price. Summarize intent, then pay:

inflow mpp pay https://api.foo.dev/dataset.csv --interval 5 --max-attempts 180 --output-file /tmp/dataset.csv --no-show-body
# Persist transaction_id from the response in case polling is interrupted.
# Returns outcome "paid" with output_saved_to /tmp/dataset.csv.

"Approval requested - confirm in the InFlow app: https://app.inflowpay.ai/approvals/appr_xyz I'll keep polling. 15-min window."

Once the result arrives:

"Paid 0.10 USDC. Transaction txn_abc. Saved the dataset to /tmp/dataset.csv."

Two-step variant (host can't block): follow Step 2's two-step path; mpp fetch polls, attaches Authorization: Payment, and returns the resource body without exposing the credential.

Worked example (x402)

A user asks the agent to fetch a paywalled article at https://api.foo.dev/article-3.

Pre-flight: inflow inspect <url> reports detected: ["x402"]; the intersection lands on exact × solana:mainnet, and the user's 100.5 USDC balance easily covers the 0.10 USDC the seller requires. Proceed.

"I'm about to pay 0.10 USDC on Solana mainnet to api.foo.dev for /article-3. Your balance is 100.5 USDC - plenty. Requesting approval next."

inflow x402 pay https://api.foo.dev/article-3 --payment-id "<stable-opaque-id>" --interval 5 --max-attempts 180
# Persist transaction_id from the response in case polling gets interrupted.
# Returns outcome "paid"; body contains the article JSON.

"Approval requested - confirm in the InFlow app: https://app.inflowpay.ai/approvals/appr_xyz I'll keep polling. 15-min window."

Once the result arrives:

"Paid 0.10 USDC. Transaction txn_abc. Server returned: 'How to brew coffee - ...'"

Two-step variant (host can't block): follow Step 2's two-step path; x402 fetch polls, attaches PAYMENT-SIGNATURE, and returns the resource body without exposing the encoded payload.

Subscribing to an MPP resource

Use this flow only when inflow inspect <url> shows an MPP challenge with intent: subscription. Before initiating it, show the user the recurring amount and currency, billing period, expiration, seller reference when present, resource URL, and settlement rail. Each subscription option includes a stable option_id derived from its recurring terms. If multiple options are available, ask the user which one they want and pass that identifier to mpp subscribe; never select the first option implicitly.

inflow mpp subscribe <url> --option-id <option_id> --interval 5 --max-attempts 180

The user approves the immutable recurring terms. Successful activation settles the first period. Later access uses subscriptions fetch, which obtains a fresh credential for the current seller challenge.

If the host cannot wait for approval, omit --interval, retain the returned transaction_id, and run the returned _next.command. mpp fetch polls, activates the subscription, and returns the resource. After activation, use subscriptions fetch <subscription_id> <url>; the server decides whether the current billing period is already paid or requires one new charge.

Manage the buyer's subscriptions with:

inflow subscriptions list
inflow subscriptions list --status active
inflow subscriptions get <subscription_id>
inflow subscriptions fetch <subscription_id> <url>
inflow subscriptions cancel <subscription_id>

Obtain explicit user confirmation immediately before cancelling a subscription. Cancellation is immediate and does not refund a paid period. A cancelled subscription cannot obtain another access credential. Treat PAST_DUE as recoverable through a later collection retry; EXPIRED, CANCELLED, REVOKED, and FAILED are terminal.

MPP errors

All errors in agent mode are JSON with code and message fields and exit code 1. MPP-specific codes (shared codes are in § Shared errors). "What to tell the user" is the prompt to surface - don't dump the raw error:

x402 errors

All errors in agent mode are JSON with code and message fields and exit code 1. x402-specific codes (shared codes are in § Shared errors). "What to tell the user" is the prompt to surface - don't dump the raw error:

Security & data handling

Applies to both protocols.

• Treat OAuth tokens and API keys as secrets - never echo them. Use Fetch for approved payments so one-time payment credentials are attached to the seller request without being pasted back to the user.
• Respect /agents.txt and /llm.txt on sites you browse.
• Avoid suspicious 402 endpoints - if the domain doesn't match what the user asked to pay, or the price is different from expectation, stop and ask.
• When displaying deposit addresses to the user, print the full address (don't truncate). Truncating breaks copy-paste.

Shared errors

These apply to both protocols (in addition to each section's protocol-specific codes). All are JSON with code and message and exit code 1. Where a command is protocol-specific, use your prefix (<mpp|x402>). "What to tell the user" is the prompt to surface - don't dump the raw error:

Out of scope

This skill covers programmatic HTTP 402 payments (MPP and x402) only. It does NOT handle:

• Traditional merchant checkouts No PANs (credit card forms, hosted checkouts).
• Card issuance or wallet management beyond balances list and deposit-addresses list.
• Refunds, disputes, chargebacks - handled out of band via support.
• Peer-to-peer transfers between users or wallets.
• FX / currency conversion. Buyer logic matches the seller's accepted rails against the account's supported assets.

For any of the above, point the user to https://app.inflowpay.ai or support.

Further docs

• MPP protocol: https://mpp.dev
• x402 protocol: https://x402.org
• InFlow: https://app.inflowpay.ai