Model Context Protocol (MCP)

Overview

The Sardis MCP Server exposes 50+ payment tools through the Model Context Protocol, enabling AI assistants like Claude Desktop, Cursor, and ChatGPT to execute secure payments, manage wallets, and enforce spending policies.

What is MCP?

The Model Context Protocol is Anthropic’s standard for connecting AI assistants to external tools and data sources. Think of it as a universal API for AI agents.

When to Use MCP

Desktop AI Assistants: Claude Desktop, ChatGPT Desktop, Windsurf
IDEs: Cursor, VS Code with MCP extension, Claude Code
No-Code Integration: Works without writing any code
Multi-Tool Workflows: Combine Sardis with other MCP servers

Installation

Claude Desktop

Edit your Claude Desktop config file:

macOS
Windows
Linux

~/Library/Application Support/Claude/claude_desktop_config.json

%APPDATA%\Claude\claude_desktop_config.json

~/.config/Claude/claude_desktop_config.json

Add the Sardis MCP server:

claude_desktop_config.json

{
  "mcpServers": {
    "sardis": {
      "command": "npx",
      "args": ["-y", "@sardis/mcp-server"],
      "env": {
        "SARDIS_API_KEY": "sk_live_your_api_key_here",
        "SARDIS_WALLET_ID": "wallet_abc123",
        "SARDIS_MODE": "live"
      }
    }
  }
}

Restart Claude Desktop to load the tools.

Cursor

Create .cursor/mcp.json in your project:

.cursor/mcp.json

{
  "mcpServers": {
    "sardis": {
      "command": "npx",
      "args": ["-y", "@sardis/mcp-server"],
      "env": {
        "SARDIS_API_KEY": "sk_live_...",
        "SARDIS_WALLET_ID": "wallet_..."
      }
    }
  }
}

Claude Code CLI

claude mcp add sardis -- npx -y @sardis/mcp-server
export SARDIS_API_KEY=sk_live_...

ChatGPT Desktop

Open Settings → MCP Servers
Click Add Custom
Enter:
- Name: sardis
- Command: npx -y @sardis/mcp-server
- Environment: SARDIS_API_KEY=sk_live_...

Available Tools

The MCP server exposes all Sardis functionality through 50+ tools:

Core Payment Tools

sardis_pay

Execute a payment with policy enforcement

sardis_get_balance

Check wallet balance and limits

sardis_check_policy

Validate payment against spending policy

sardis_list_transactions

View transaction history

Hold Management (Pre-Authorization)

Tool	Description
`sardis_create_hold`	Reserve funds for future payment
`sardis_capture_hold`	Capture reserved funds
`sardis_void_hold`	Cancel a hold and release funds
`sardis_release_hold`	Release hold without capture
`sardis_extend_hold`	Extend hold expiration

Agent & Wallet Management

Tool	Description
`sardis_create_agent`	Register a new AI agent
`sardis_create_wallet`	Create non-custodial MPC wallet
`sardis_list_agents`	List all registered agents
`sardis_list_wallets`	List all wallets

Virtual Cards

Tool	Description
`sardis_issue_card`	Issue virtual card for agent
`sardis_freeze_card`	Temporarily freeze card
`sardis_unfreeze_card`	Unfreeze a card
`sardis_cancel_card`	Permanently cancel card

Spending Analytics

Tool	Description
`sardis_get_spending_summary`	Get spending totals by period
`sardis_get_spending_by_vendor`	Vendor spending breakdown
`sardis_get_spending_by_category`	Category spending analysis
`sardis_get_spending_trends`	Identify spending patterns

Group Budgets

Tool	Description
`sardis_create_group`	Create agent group with shared budget
`sardis_add_agent_to_group`	Add agent to spending group
`sardis_get_group_spending`	Check group budget usage

Approvals

Tool	Description
`sardis_request_approval`	Request human approval for payment
`sardis_check_approval`	Check approval status
`sardis_list_pending_approvals`	List pending approval requests

Fiat On/Off Ramps

Tool	Description
`sardis_fund_wallet`	Fund wallet via ACH/wire
`sardis_withdraw_to_bank`	Withdraw to bank account
`sardis_onramp_fiat_to_usdc`	Convert USD to USDC
`sardis_offramp_usdc_to_fiat`	Convert USDC to USD

View the complete list of 50+ tools in the MCP Tools Reference.

Example Conversations

Once configured, your AI assistant can handle payment tasks naturally:

You: Check my wallet balance and pay $50 to OpenAI for API credits

Claude:
→ Using sardis_get_balance
  Balance: 1,000 USDC on Base
  Remaining daily limit: $500

→ Using sardis_check_policy
  Payment allowed: ✓
  Within limits: ✓

→ Using sardis_pay
  ✓ Paid $50 USDC to openai.com
  TX: 0x7f3b...a2c9
  Chain: Base
  Status: Confirmed

Your payment of $50 to OpenAI has been processed successfully.

Configuration

Environment Variables

Variable	Required	Default	Description
`SARDIS_API_KEY`	Yes	-	Your Sardis API key (get one)
`SARDIS_WALLET_ID`	No	-	Default wallet for operations
`SARDIS_AGENT_ID`	No	-	Agent ID for attribution
`SARDIS_MODE`	No	`sandbox`	`live` or `sandbox`
`SARDIS_CHAIN`	No	`base`	Default chain (base, polygon, ethereum)
`SARDIS_API_URL`	No	`https://api.sardis.sh`	API endpoint

Sandbox Mode (No API Key Needed)

Test Sardis without real funds using sandbox mode:

{
  "mcpServers": {
    "sardis": {
      "command": "npx",
      "args": ["-y", "@sardis/mcp-server", "--demo"],
      "env": {
        "SARDIS_MODE": "sandbox"
      }
    }
  }
}

No API key required. All operations are simulated.

Policy Configuration

Enforce spending policies via environment variables:

{
  "env": {
    "SARDIS_API_KEY": "sk_live_...",
    "SARDIS_POLICY_BLOCKED_VENDORS": "gambling.com,casino.net",
    "SARDIS_POLICY_ALLOWED_VENDORS": "openai.com,anthropic.com,aws.com",
    "SARDIS_REQUIRE_EXPLICIT_APPROVAL": "true"
  }
}

Resources

The MCP server exposes wallet data through resources:

Resource URI	Description
`sardis://wallet/balance`	Current balance and limits
`sardis://wallet/info`	Wallet configuration
`sardis://config`	Server configuration status
`sardis://tools`	List of all available tools

Access resources with:

You: Read sardis://wallet/balance

Prompts

Use built-in prompts for common workflows:

Prompt	Description
`pay-vendor`	Make a payment with policy checks
`check-balance`	Check balance and limits
`sandbox-tour`	Guided tour of sandbox features

Invoke with:

You: Use the pay-vendor prompt for $50 to OpenAI

Rate Limiting

The MCP server enforces per-tool rate limits to prevent abuse:

Tool Category	Limit
Payment execution	5 calls/minute
Wallet mutations	3 calls/minute
Hold operations	10 calls/minute
Read operations	60 calls/minute

Security

Non-Custodial

All wallets use Turnkey MPC. Private keys never exist in a single location.

Policy Enforcement

Every transaction validated against:

Per-transaction limits
Daily/monthly spending caps
Merchant allowlists/blocklists
Category restrictions

Audit Trail

All operations logged to append-only ledger for compliance.

Troubleshooting

Tools Not Appearing

Restart your MCP client after config changes
Verify JSON syntax (no trailing commas)
Check that npx is in your PATH
View logs: tail -f ~/Library/Logs/Claude/mcp*.log (macOS)

API Key Errors

Error: Invalid API key

Verify your API key at sardis.sh/settings/api-keys

Rate Limit Exceeded

Rate limit exceeded for sardis_pay. Maximum 5 calls per minute.

Wait 60 seconds or optimize your agent’s logic to batch operations.

Next Steps

API Reference

Full documentation of all 50+ MCP tools

Build Agents

Learn how to build autonomous payment agents

Policy Engine

Understand spending policy enforcement

SDKs

Use Sardis in your own agent frameworks

Get Started

Core Concepts

Framework Integrations

Guides

Blockchain

Security

​Overview

What is MCP?

​When to Use MCP

​Installation

​Claude Desktop

​Cursor

​Claude Code CLI

​ChatGPT Desktop

​Available Tools

​Core Payment Tools

sardis_pay

sardis_get_balance

sardis_check_policy

sardis_list_transactions

​Hold Management (Pre-Authorization)

​Agent & Wallet Management

​Virtual Cards

​Spending Analytics

​Group Budgets

​Approvals

​Fiat On/Off Ramps

​Example Conversations

​Configuration

​Environment Variables

​Sandbox Mode (No API Key Needed)

​Policy Configuration

​Resources

​Prompts

​Rate Limiting

​Security

​Non-Custodial

​Policy Enforcement

​Audit Trail

​Troubleshooting

​Tools Not Appearing

​API Key Errors

​Rate Limit Exceeded

​Next Steps

API Reference

Build Agents

Policy Engine

SDKs

Build docs developers (and LLMs) love

Overview

When to Use MCP

Installation

Claude Desktop

Cursor

Claude Code CLI

ChatGPT Desktop

Available Tools

Core Payment Tools

Hold Management (Pre-Authorization)

Agent & Wallet Management

Virtual Cards

Spending Analytics

Group Budgets

Approvals

Fiat On/Off Ramps

Example Conversations

Configuration

Environment Variables

Sandbox Mode (No API Key Needed)

Policy Configuration

Resources

Prompts

Rate Limiting

Security

Non-Custodial

Policy Enforcement

Audit Trail

Troubleshooting

Tools Not Appearing

API Key Errors

Rate Limit Exceeded

Next Steps