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Paid MCP Tool

The paid MCP tool example demonstrates a resource that is discoverable and callable by agents through LumenBazaar MCP workflows.

Example location:

lumenbazaar-backend/apps/examples/paid-mcp-tool

Purpose​

This example should prove:

  • MCP tool metadata can be cataloged.
  • Agents can search paid tools.
  • Agents can inspect deterministic tool schemas.
  • Agents can call the tool with a budget cap.
  • The result includes receipt and transaction evidence.

Tool Shape​

Example tool:

summarize_dataset

Input schema:

{
  "type": "object",
  "properties": {
    "datasetUrl": {
      "type": "string"
    },
    "maxRows": {
      "type": "integer",
      "minimum": 1,
      "maximum": 1000
    }
  },
  "required": ["datasetUrl"]
}

Output schema:

{
  "type": "object",
  "properties": {
    "summary": {
      "type": "string"
    },
    "receipt": {
      "type": "object"
    }
  },
  "required": ["summary", "receipt"]
}

Payment Terms​

Default testnet terms:

network: stellar:testnet
asset: USDC
amount: 0.15
scheme: exact

MCP Flow​

Agent flow:

  1. Call list_supported_networks.
  2. Call search_paid_resources.
  3. Call inspect_resource.
  4. Check budget through inspect_budget.
  5. Call prepare_payment.
  6. Call call_paid_resource.
  7. Store the returned receipt.

Expected Tool Call​

{
  "resourceId": "mcp_resource_id",
  "input": {
    "datasetUrl": "https://example.com/data.csv",
    "maxRows": 100
  },
  "maxAmount": "0.20"
}

Acceptance Criteria​

  • MCP example server starts locally.
  • Tool metadata is valid.
  • Tool appears in discovery.
  • Agent can inspect schemas.
  • Budget controls prevent overspending.
  • Paid testnet call succeeds.
  • Tool output includes result, receipt, and transaction hash.
  • Stable errors are returned for budget, schema, payment, and settlement failures.

Evidence​

Record:

  • MCP tool name.
  • Resource ID.
  • Receipt ID.
  • Transaction hash.
  • Ledger.
  • Network.
  • Asset.
  • Amount.
  • MCP tool call input.