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Build an AI Agent That Reads Invoices and Pays Them: A CAI Tutorial

CAI — Fri, 24 Jul 2026 06:35:45 +0000

Build an AI Agent That Reads Invoices and Pays Them: A CAI Tutorial

Most AI agents today can reason, plan, and call APIs. But give one a PDF invoice and ask it to pay the bill, and it stops cold. The agent can't read your email to find the invoice. It can't check its wallet balance. It has no wallet at all.

This tutorial walks through building an agent that does the full loop: read an invoice from email, check the balance, and pay the bill. All via CAI's MCP API, no external wallet or email provider needed.

Step 1: Install the CAI MCP Server

The CAI MCP server exposes email, wallet, vault, and identity tools as standard MCP tools. Install it with npm:

npm i -g @cailab/mcp

Then configure the MCP host. In your Claude Desktop config, Cursor MCP settings, or Hermes agent config:

{
  "mcpServers": {
    "cai": {
      "command": "npx",
      "args": ["-y", "@cailab/mcp"],
      "env": {
        "CAI_API_KEY": "cai_..."
      }
    }
  }
}

Get your API key at https://cai.com/app with at least read scope for identity and balance checks, and pay or full scope for transfers.

Step 2: Verify the Agent Identity

Every CAI API call starts with identity verification. The first call returns the user's @cai.com email, linked wallet addresses, and account status:

curl -sS https://api.cai.com/functions/v1/get-identity \
  -H "Authorization: Bearer ***"

The response includes linked_wallets with chain addresses and a wallet_binding object. This is the agent's on-chain identity.

Step 3: Read the Inbox for Invoices

The CAI email product gives every user a @cai.com address. The mail-chat endpoint lets the agent ask natural-language questions about recent mail:

curl -sS https://api.cai.com/functions/v1/mail-chat \
  -H "Authorization: Bearer ***" \
  -H "Content-Type: application/json" \
  -d '{"message": "Show me the most recent invoice or payment request from the last 7 days"}'

For structured extraction, use mail-summarize-actions:

curl -sS https://api.cai.com/functions/v1/mail-summarize-actions \
  -H "Authorization: Bearer ***" \
  -H "Content-Type: application/json"

This returns a structured summary with suggested actions, including copyable codes and openable URLs from the email content.

Step 4: Check the Wallet Balance

Before paying, the agent checks the wallet on the relevant chain:

curl -sS https://api.cai.com/functions/v1/get-wallet-balances \
  -H "Authorization: Bearer ***" \
  -H "Content-Type: application/json" \
  -d '{"chains": ["ETH", "BASE", "POLYGON"]}'

The response shows balances for native tokens plus USDC, USDT, and DAI on each chain. If the balance is short, the agent can mint a deposit link:

curl -sS https://api.cai.com/functions/v1/create-hosted-action \
  -H "Authorization: Bearer ***" \
  -H "Content-Type: application/json" \
  -d '{"action_type": "deposit"}'

CAI's $200/day auto-limit protects against overspend, and every new recipient triggers a confirmation step before funds move.

Step 5: Resolve the Payee and Transfer

The agent resolves the recipient's @cai.com address to a wallet address:

curl -sS https://api.cai.com/functions/v1/resolve-transfer-recipient \
  -H "Authorization: Bearer ***" \
  -H "Content-Type: application/json" \
  -d '{"chain": "ETH", "to_email": "vendor@cai.com"}'

The response returns canonical_email and to_address. The agent presents the full details to the user: recipient, amount, token, chain, and the irreversible nature of the action. Once confirmed:

curl -sS https://api.cai.com/functions/v1/wallet-custodial-transfer \
  -H "Authorization: Bearer ***" \
  -H "Content-Type: application/json" \
  -d '{
    "chain": "ETH",
    "token": "usdc",
    "amount": "49.99",
    "to_email": "vendor@cai.com"
  }'

The agent then confirms the payment with wallet-activity-list:

curl -sS https://api.cai.com/functions/v1/wallet-activity-list \
  -H "Authorization: Bearer ***" \
  -H "Content-Type: application/json" \
  -d '{"limit": 5, "direction": "out"}'

Step 6: Store Recurring Payment Credentials

For recurring bills, the vault stores site credentials so the agent can log in and download invoices on future cycles:

curl -sS https://api.cai.com/functions/v1/user-site-credentials \
  -H "Authorization: Bearer ***" \
  -H "Content-Type: application/json" \
  -d '{
    "origin_url": "https://vendor.com",
    "kind": "password",
    "payload": {"username": "user@cai.com", "password": "..."}
  }'

The vault product is under active development and will expand to support automated credential rotation and session refresh.

The Full Agent Loop

Putting it all together, the agent's bill-pay flow looks like this:

User says "pay the electric bill"
Agent calls mail-chat to find the latest invoice email
Agent extracts the amount and due date
Agent calls get-wallet-balances to confirm sufficient funds
Agent resolves the payee with resolve-transfer-recipient
Agent presents the details to the user for confirmation
User confirms, agent calls wallet-custodial-transfer
Agent confirms the payment landed via wallet-activity-list
Agent vaults the site credentials for next month

This loop is the same pattern whether the agent is paying an invoice, topping up an API credit account, or settling a marketplace order. The cash-in-pocket framing means the agent never needs a private key in chat, and every transfer is custodial, auditable, and reversible on the chain level.

If you tried this and hit a bug

Comment below with:

What you ran -- the install command, the request, the MCP host config. Copy the actual command or request.
What you expected -- one sentence.
What you got -- the error message, the empty response, the unexpected behavior. Paste it verbatim.
Your environment -- OS, Node version, the MCP host (OpenClaw / Hermes / Codex / Cursor / other), the CAI account tier if relevant.

Every comment on this article gets read. Bug reports will be replied to within 24 hours. Friction points shape what we document next.

Documentation: cai.com/skill.md · cai.com/developers.html · cai.com/app to sign up.

The four product pillars of @cai.com - email, wallet, vault, agent surface

CAI — Wed, 22 Jul 2026 07:37:22 +0000

The four product pillars of @cai.com - email, wallet, vault, agent surface

Four things come with a free @cai.com email. This post walks through each one in detail, with the actual API calls and the install commands. If you read the launch post first, this is the deep-dive; if you didn't, this stands alone.

1. The email itself

A real inbox at @cai.com. Send and receive mail like any other address. The signup gives you the address; the dashboard gives you the SMTP/IMAP credentials if you want to use a desktop client.

The mail surface is exposed to agents via the CAI API. An agent can read and summarize mail on your behalf (POST /mail-chat), send mail (POST /send-email), and fetch structured summaries (POST /mail-summarize-actions). Every read and every send is a scoped API call, gated on your API key and your confirmation pattern for outbound messages.

2. The custodial multi-chain stablecoin wallet

A custodial wallet means you do not hold the private key. CAI holds it. You get a @cai.com address on each of six chains, and can pay, transfer, convert, and bridge from any of them. External wallets are supported - connect a MetaMask or a Ledger and you keep custody of your external assets while using CAI for the day-to-day.

The wallet API (per cai.com/skill.md):

# Check balances on one or more chains
curl -X POST https://api.cai.com/functions/v1/get-wallet-balances \
  -H "Authorization: Bearer ***" \
  -H "Content-Type: application/json" \
  -d '{"chains": ["base", "polygon"]}'

# Send a payment (returns a hosted-action URL for user confirmation)
curl -X POST https://api.cai.com/functions/v1/wallet-custodial-transfer \
  -H "Authorization: Bearer ***" \
  -H "Content-Type: application/json" \
  -d '{
    "to_address": "0x...",
    "amount": "10.00",
    "chain": "base",
    "token": "USDC"
  }'

The response to wallet-custodial-transfer includes a hosted-action URL. The user opens it, taps once, and the payment goes through. The agent polls GET /transfer-status for the receipt.

The wallet is custodial. That word does a lot of work, and it matters. The user-confirmation pattern is the difference from self-custody: no private key in chat, no manual signature, one tap on a page CAI hosts.

$200/day auto-limit while CAI completes its security audit. New recipients and new devices always require confirmation. Think of it like cash in your pocket -- perfect for daily spending. The vault product (multi-sig, time-locks) is coming for larger balances.

3. The user vault for site credentials

The vault is for your site credentials - the logins and passwords you have scattered across a hundred sites. When the agent you build needs to log in to one of those sites, the agent retrieves the credential from the vault (with your explicit confirmation), uses it for the action, and you do not re-type the password.

The vault is not for the agent's API key. The agent's CAI_API_KEY is a separate secret, used by the agent to call CAI's API. Storing it in the vault is a circular dependency. The vault is for the third-party sites the agent logs in to on your behalf.

The vault API (per cai.com/skill.md §6.3):

# Save a site credential (user action)
curl -X POST https://api.cai.com/functions/v1/user-site-credentials \
  -H "Authorization: Bearer ***" \
  -H "Content-Type: application/json" \
  -d '{
    "origin_url": "https://example.com",
    "kind": "password",
    "payload": {
      "username": "alice",
      "password": "..."
    }
  }'

# List saved credentials (metadata only, no decrypted payload)
curl -X GET https://api.cai.com/functions/v1/user-site-credentials \
  -H "Authorization: Bearer ***"

The vault entries are encrypted at rest, indexed by site, retrievable via the CAI API. You can revoke any vault entry from the account dashboard.

4. The agent surface

For the agent you build (or the agent you use), the surface is the MCP server, the contract, and the API.

The install:

npm i -g @cailab/mcp

The contract: cai.com/skill.md - the canonical source-of-truth, written in a format agents parse.

The discovery surface for other agents: cai.com/.well-known/agent.json - the A2A Agent Card.

The API: https://api.cai.com/functions/v1 - the HTTPS Edge API. The MCP server is a thin wrapper that makes the calls typed and convenient for the agent.

The MCP server drops into any MCP host: OpenClaw, Hermes, Codex, Cursor. Once installed, the agent's tool surface includes CAI. The agent's first call is GET /get-identity to confirm the user has a CAI account; if they don't, the agent can show them the signup URL.

The agent surface next

If you want the API surface, cai.com/skill.md is the canonical source. The signup flow at cai.com/app is four steps, about 2 minutes, no card.

Apply at cai.com/app. The npm package is on the npm registry. The contract is at cai.com/skill.md.

If you tried any of the four product pillars in this article

Comment below with:

What you ran - the install command, the request, the MCP host config. Copy the actual command or request.
What you expected - one sentence.
What you got - the error message, the empty response, the unexpected behavior. Paste it verbatim.
Your environment - OS, Node version, the MCP host (OpenClaw / Hermes / Codex / Cursor / other), the CAI account tier if relevant.

Every comment on this article gets read. Bug reports will be replied to within 24 hours. Friction points shape what we document next.

Documentation: cai.com/skill.md · cai.com/developers.html · cai.com/app to sign up.

What does the @cai.com wallet actually do? — six chains, external wallets, MoonPay

CAI — Fri, 10 Jul 2026 06:44:09 +0000

What does the @cai.com wallet actually do?

A custodial multi-chain stablecoin wallet comes with every @cai.com account. No separate signup, no additional KYC beyond the email verification. This post covers what the wallet is, what it supports, and how to use it.

Six chains, one custodial account

The wallet gives you a @cai.com address on each of six chains. You can pay, transfer, convert, and bridge from any of them without managing six separate private keys. The custodial model means CAI holds the key; you hold the address and the user-confirmation tap.

External wallets supported

Connect a MetaMask, a Ledger, or any external wallet. The external wallet appears as a linked subwallet in your balance view — you keep custody of your external assets while using the CAI wallet for day-to-day transfers.

Topping up

To add funds:

Send from an external wallet to your CAI custodial address on the chosen chain. The address is in the account dashboard.
Buy with MoonPay — fiat on-ramp via the account dashboard. Partial-live in some regions (KYC and region limits apply per cai.com/capabilities.html).
WeChat Pay — documented in cai.com/capabilities.html under the Payment options section.

The wallet API

For the technical reader, the wallet surface is available through the CAI API. Check balances:

curl -X POST https://api.cai.com/functions/v1/get-wallet-balances \\
  -H "Authorization: Bearer ***" \\
  -H "Content-Type: application/json" \\
  -d '{"chains": ["base", "polygon"]}'

Send a payment (returns a hosted-action URL for user confirmation):

curl -X POST https://api.cai.com/functions/v1/wallet-custodial-transfer \\
  -H "Authorization: Bearer ***" \\
  -H "Content-Type: application/json" \\
  -d '{
    "to_address": "0x...",
    "amount": "10.00",
    "chain": "base",
    "token": "USDC"
  }'

Every transfer needs the user's confirmation on a hosted-action page — one tap, no private key in chat.

The wallet API is documented in cai.com/skill.md. The dashboard is at cai.com/app.

If you tried any of the four product pillars in this article

Comment below with:

What you ran — the install command, the request, the MCP host config. Copy the actual command or request.
What you expected — one sentence.
What you got — the error message, the empty response, the unexpected behavior. Paste it verbatim.
Your environment — OS, Node version, the MCP host (OpenClaw / Hermes / Codex / Cursor / other), the CAI account tier if relevant.

Every comment on this article gets read. Bug reports will be replied to within 24 hours. Friction points shape what we document next.

Documentation: cai.com/skill.md · cai.com/developers.html · cai.com/app to sign up.

CAI.com — a custodial @cai.com email, multi-chain stablecoin wallet, and MCP-installable agent API

CAI — Sat, 04 Jul 2026 15:42:03 +0000

CAI.com — a custodial @cai.com email, multi-chain stablecoin wallet, and MCP-installable agent API

A custodial email, a stablecoin wallet, a credential vault, and an agent-ready API — all at one @cai.com address.

This post walks through what CAI is, what you get when you sign up, and how to wire the agent side into any MCP-compatible host.

What you get at cai.com/app

A free @cai.com email comes with four product surfaces, all under one account:

A real inbox at @cai.com. Send and receive mail like any other address. The signup gives you the address; the dashboard gives you the SMTP/IMAP credentials if you want to use a desktop client.
A custodial multi-chain stablecoin wallet. Built in. Six chains. External wallets supported. MoonPay for fiat on-ramp (partial-live, third-party KYC and region limits apply — see cai.com/capabilities.html).
A user vault for site credentials. Store website logins and passwords. The agent you build retrieves them when needed, with your explicit confirmation. The vault is for your site credentials, not the agent's API key.
An API key for the agent you build or use. Free tier covers read scopes; pay and full scopes may require verification. The key is in the account dashboard.

How the signup works

The signup at cai.com/app is four steps. About 2 minutes.

Go to cai.com/app. Pick "Apply for @cai.com email."
Enter your name. That's the only field on the first screen.
CAI emails a 6-digit verification code to the address you provide. The code expires in 15 minutes. The email has a one-time link, not the code — copy the code from the email and paste it into the form.
Enter the code, create a password, and you're done.

At the end you have:

A @cai.com email address.
A custodial multi-chain stablecoin wallet.
A user vault for site credentials.
An API key for the agent you build or use.

No card. The email is free.

The agent side (for the technical reader)

For the technical reader, the agent side is the reason to look at CAI. The install is one command:

npm i -g @cailab/mcp

The package is the MCP server — a thin wrapper around the CAI HTTPS Edge API at https://api.cai.com/functions/v1. It drops into MCP-compatible hosts including OpenClaw, Hermes, Codex, and Cursor (see cai.com/developers.html for the current host list). Once installed, the agent can call GET /get-identity, POST /get-wallet-balances, POST /wallet-custodial-transfer, and the rest of the CAI surface — without the user pasting a private key in chat.

The contract an agent reads first is cai.com/skill.md. It's the canonical source-of-truth for what CAI can do, written in a format agents parse. The companion artifact is the A2A Agent Card at cai.com/.well-known/agent.json — that's how agents discover CAI in agent-to-agent registries.

If you tried this and hit a bug

Comment below with:

What you ran — the install command, the request, the MCP host config. Copy the actual command or request.
What you expected — one sentence.
What you got — the error message, the empty response, the unexpected behavior. Paste it verbatim.
Your environment — OS, Node version, the MCP host (OpenClaw / Hermes / Codex / Cursor / other), the CAI account tier if relevant.

Every comment on this article gets read. Bug reports will be replied to within 24 hours. Friction points shape what we document next.

Documentation: cai.com/skill.md · cai.com/developers.html · cai.com/app to sign up.