MCP (Model Context Protocol)

The Model Context Protocol (MCP) lets you connect external tool servers to Sempleo agents. MCP servers expose tools that agents can use alongside built-in capabilities — no custom integration code required.

What Is MCP?

MCP is an open protocol for connecting AI models to external tools and data. An MCP server is a lightweight service that:

• Exposes tools — Functions that agents can call (e.g., query a PIM, look up inventory, create records)
• Provides resources — Read-only data sources (e.g., product catalog, configuration)
• Defines prompts — Pre-configured prompt templates for common tasks

Use Cases

• PIM / ERP integration — Connect your Product Information Management or ERP system so agents can look up product data, inventory, orders
• CRM sync — Give agents access to customer records, deals, activities from any CRM
• Custom databases — Expose internal databases through a secure MCP server
• Industry-specific tools — Connect domain-specific calculation engines, validators, or APIs
• Any REST API — Wrap existing APIs in a thin MCP layer for universal agent access

Setup

1. Deploy an MCP Server

Your MCP server can be:

• A standalone service deployed alongside your infrastructure
• A containerized service running in your cloud
• A serverless function (AWS Lambda, Google Cloud Functions)
• An open-source community MCP server from npmjs.com or GitHub

2. Add in Sempleo

1. Go to Integrations page
2. Scroll to the External Data Sources (MCP) section
3. Click Add Server
4. Enter a name, server URL, optional description
5. Choose the authentication type:
   • None — No authentication required
   • Bearer Token — Standard Authorization: Bearer <token> header
   • API Key — Sent as X-API-Key header
   • Custom Header — You specify the header name
6. Click Add Server — Sempleo automatically tests the connection and discovers tools

3. Test the Connection

After adding a server, use the Test Connection button to verify:

• The server is reachable
• Authentication is valid
• Tools can be discovered

The detail sheet shows all discovered tools with their names, descriptions, and input schemas.

4. Assign to Agents

Once connected, you can assign MCP servers to specific agents:

1. Open an agent's Settings page
2. Find the External Data Sources (MCP) card
3. Toggle on the servers you want this agent to access
4. The agent will have access to all tools from enabled servers

Plan Limits

Runtime Behavior

Tool Discovery Caching

Tool definitions are cached for 5 minutes. When a server is temporarily unreachable, the last known tool list is used. Use Refresh Tools to force a fresh discovery.

Circuit Breaker

If an MCP server fails 3 consecutive requests, Sempleo automatically pauses requests for 60 seconds before retrying. This prevents cascading failures.

Rate Limiting

Each MCP server has a configurable rate limit (default: 60 requests/minute). This protects both Sempleo and the MCP server from overload.

Response Size Protection

MCP responses exceeding 512KB are automatically truncated to prevent memory issues.

Security

• Authentication tokens are encrypted at rest using AES-256-GCM
• All MCP tool calls are logged in the audit trail with timing data
• Governance policies support blocking MCP tools:
  • Block specific tools: add mcp_servername_toolname to blocked tools list
  • Block all tools from a server: use wildcard mcp_servername_*
  • Block all MCP tools: enable the blockMcpTools rule
• Approval gates apply to MCP tools the same way as built-in tools
• HTTPS is strongly recommended — the UI warns when using HTTP

Governance

Workspace admins can control MCP tool access through governance policies:

• Tool Restriction policies apply to MCP tools using their full prefixed name (mcp_<server_name>_<tool_name>)
• Wildcard patterns let you block/allow groups of tools (e.g., mcp_salesforce_*)
• The Block All MCP Tools setting (blockMcpTools) provides a kill switch
• All MCP server add/remove/test actions are recorded in the audit log

Building an MCP Server

For guidance on building your own MCP server, see the MCP specification.

A minimal MCP server needs:

1. A tool registry — responds to tools/list with available tools and their input schemas
2. A tool executor — responds to tools/call with results
3. An HTTP endpoint that speaks JSON-RPC 2.0

Minimal Example (Node.js)

import express from 'express';
 
const app = express();
app.use(express.json());
 
app.post('/', (req, res) => {
  const { method, params, id } = req.body;
 
  if (method === 'tools/list') {
    return res.json({
      jsonrpc: '2.0', id,
      result: { tools: [
        { name: 'lookup_product', description: 'Look up a product by SKU',
          inputSchema: { type: 'object', properties: { sku: { type: 'string' } }, required: ['sku'] } }
      ] }
    });
  }
 
  if (method === 'tools/call' && params.name === 'lookup_product') {
    // Your business logic here
    return res.json({
      jsonrpc: '2.0', id,
      result: { content: [{ type: 'text', text: JSON.stringify({ name: 'Widget', price: 29.99 }) }] }
    });
  }
 
  res.json({ jsonrpc: '2.0', id, error: { code: -32601, message: 'Method not found' } });
});
 
app.get('/', (_, res) => res.json({ status: 'ok' }));
app.listen(3100);

Troubleshooting