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SignedData

Connect Claude to an MCP server

This tutorial walks through giving Claude Desktop access to signed CDS data via the Model Context Protocol. We’ll connect to the hosted finance and commodities servers, then optionally point Claude at a locally-running lottery server.

Prerequisites

Section titled “Prerequisites”
  • Claude Desktop installed
  • The Claude Desktop config file location:
    • macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
    • Linux: ~/.config/claude/claude_desktop_config.json
    • Windows: %APPDATA%\Claude\claude_desktop_config.json

Hosted servers (zero install)

Section titled “Hosted servers (zero install)”

The fastest path: point Claude at the deployed MCP endpoints. Nothing to install locally.

  1. Open your Claude Desktop config file

    Create it if it does not exist. The starting content is {}.

  2. Add the hosted servers

    {
      "mcpServers": {
        "signeddata-finance": {
          "url": "https://finance.mcp.signed-data.org/mcp"
        },
        "signeddata-commodities": {
          "url": "https://commodities.mcp.signed-data.org/mcp"
        },
        "signeddata-companies": {
          "url": "https://companies.mcp.signed-data.org/mcp"
        }
      }
    }

  3. Restart Claude Desktop

    Close and reopen the app. The MCP servers connect on launch.

  4. Test from a Claude conversation

    Try prompts like:

    • “What is the current SELIC rate?”
    • “Show me the latest soja futures from B3.”
    • “Look up CNPJ 33.000.167/0001-01.”

    Claude will call the appropriate signed tool and return the verified data.

Local server (Python install)

Section titled “Local server (Python install)”

If you prefer to run the MCP server locally — for development, custom signing, or air-gapped environments — install the package and point Claude at the command.

  1. Install the SDK and an MCP server

    Terminal window
    pip install signeddata-cds
    pip install signeddata-mcp-lottery

    Replace mcp-lottery with mcp-finance, mcp-commodities, or mcp-companies for the others.

  2. (Optional) Generate signing keys

    The hosted servers always sign. The local server signs only if you provide keys.

    Terminal window
    python3 -c "
    from cds import generate_keypair
    import os; os.makedirs('keys', exist_ok=True)
    generate_keypair('keys/private.pem', 'keys/public.pem')
    "

  3. Configure Claude Desktop

    {
      "mcpServers": {
        "signeddata-lottery": {
          "command": "signeddata-mcp-lottery",
          "env": {
            "CDS_PRIVATE_KEY_PATH": "/absolute/path/to/keys/private.pem",
            "CDS_PUBLIC_KEY_PATH":  "/absolute/path/to/keys/public.pem",
            "CDS_ISSUER":           "https://myorg.example.com"
          }
        }
      }
    }

  4. Restart Claude Desktop and try it

    “What were the last five Mega Sena draws?”

Mixing hosted and local

Section titled “Mixing hosted and local”

You can combine both styles in one config file. Local servers are useful for prototyping new ingestors; hosted servers are useful for everything else.

{
  "mcpServers": {
    "signeddata-finance":     { "url": "https://finance.mcp.signed-data.org/mcp" },
    "signeddata-commodities": { "url": "https://commodities.mcp.signed-data.org/mcp" },
    "signeddata-lottery": {
      "command": "signeddata-mcp-lottery",
      "env": { "CDS_ISSUER": "https://myorg.example.com" }
    }
  }
}

Verification on the consumer side

Section titled “Verification on the consumer side”

Claude itself does not verify CDS signatures — it trusts the MCP server it connects to. If you need end-to-end verification (i.e., Claude’s response contains a signed envelope you can re-verify), use the cds_event_verify helper tool exposed by some servers, or capture the MCP response in your own code and call CDSVerifier.verify() on it. See the verify tutorial.