Lab 7 · MCP-style tool protocol

Tool discovery via a manifest

The Agent Lab already has tool implementations, Zod arg schemas, and a permission policy in three separate modules. Model Context Protocol takes those and renders them as one machine-readable manifest so any compatible client can discover what is available, what it requires, and what it costs in approval.

Why this lab matters: Tools need descriptions, schemas, and permission metadata to be discoverable. MCP is about tool interoperability, not magic intelligence — the same five tools below could be served from any MCP-compatible host and consumed by any MCP-compatible client.

getCustomer

Resolve a customer name or id into the canonical customer record.

read-only

Permission

Read-only data lookup. Safe to call without approval.

Input schema

{
  "type": "object",
  "properties": {
    "customerNameOrId": {
      "type": "string",
      "minLength": 1
    }
  },
  "required": [
    "customerNameOrId"
  ],
  "additionalProperties": false
}

Simulated MCP handshake

What an agent would send and receive on first contact: initialize → tools/list → tools/call. No real socket; the lab generates the envelopes from the same manifest the runner already uses.

1. initializeclient→server

{
  "protocolVersion": "2024-11-05",
  "clientInfo": {
    "name": "agent-lab-runner",
    "version": "0.1.0"
  },
  "capabilities": {}
}

2. initialize/resultserver→client

{
  "protocolVersion": "2024-11-05",
  "serverInfo": {
    "name": "agent-lab-mock-erp",
    "version": "0.1.0"
  },
  "capabilities": {
    "tools": {
      "listChanged": false
    }
  }
}

3. tools/listclient→server
```
{}
```

4. tools/list/resultserver→client

{
  "tools": [
    {
      "name": "getCustomer",
      "description": "Resolve a customer name or id into the canonical customer record.",
      "inputSchema": {
        "type": "object",
        "properties": {
          "customerNameOrId": {
            "type": "string",
            "minLength": 1
          }
        },
        "required": [
          "customerNameOrId"
        ],
        "additionalProperties": false
      }
    },
    {
      "name": "getCreditStatus",
      "description": "Return the current credit limit, exposure, available credit, status, and risk level.",
      "inputSchema": {
        "type": "object",
        "properties": {
          "customerId": {
            "type": "string",
            "minLength": 1,
            "maxLength": 64
          }
        },
        "required": [
          "customerId"
        ],
        "additionalProperties": false
      }
    },
    {
      "name": "getOpenInvoices",
      "description": "List all open and overdue invoices for a customer.",
      "inputSchema": {
        "type": "object",
        "properties": {
          "customerId": {
            "type": "string",
            "minLength": 1,
            "maxLength": 64
          }
        },
        "required": [
          "customerId"
        ],
        "additionalProperties": false
      }
    },
    {
      "name": "checkOrderEligibility",
      "description": "Compute whether a proposed order can be released given current credit and aging.",
      "inputSchema": {
        "type": "object",
        "properties": {
          "customerId": {
            "type": "string",
            "minLength": 1,
            "maxLength": 64
          },
          "orderAmount": {
            "type": "integer",
            "maximum": 10000000,
            "exclusiveMinimum": 0
          }
        },
        "required": [
          "customerId",
          "orderAmount"
        ],
        "additionalProperties": false
      }
    },
    {
      "name": "createCreditReviewTicket",
      "description": "Create a persistent credit-review ticket. Write action; always requires approval.",
      "inputSchema": {
        "type": "object",
        "properties": {
          "customerId": {
            "type": "string",
            "minLength": 1,
            "maxLength": 64
          },
          "reason": {
            "type": "string",
            "minLength": 8
          }
        },
        "required": [
          "customerId",
          "reason"
        ],
        "additionalProperties": false
      }
    }
  ]
}

5. tools/callclient→server

{
  "name": "getCustomer",
  "arguments": {
    "customerNameOrId": "ACME"
  }
}