MCP server

​

Authentication

• OAuth — for hosted clients like claude.ai and ChatGPT. Add the endpoint URL in your assistant’s connector settings; it walks you through signing in with your normal LAC portal account (Google) and authorizing. On the consent screen you pick which business the connection is for — accounts with access to multiple businesses choose one business per connection. OAuth connections act with operator access: they can read the books and statements, upload documents, draft and send invoices, and message Björn — never approve payroll, change company settings, or manage access or keys, no matter your own portal role.
• Portal API key — for clients that send custom headers (Claude Code, Cursor, VS Code, the OpenAI Responses API, anything speaking streamable HTTP). Create one in Settings → API access (see getting started) and send it as a bearer token. Like OAuth connections, keys are minted per business. The tools you see follow the key’s scope: read-scope keys see only the read tools; write-scope keys see all 31.

​

Connect a client

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claude.ai (web)

https://api.app.lastaccountingcompany.com/mcp

​

ChatGPT (web)

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Claude Code

claude mcp add --transport http lac \
  https://api.app.lastaccountingcompany.com/mcp \
  --header "Authorization: Bearer lac_sk_..."

​

Cursor

{
  "mcpServers": {
    "lac": {
      "url": "https://api.app.lastaccountingcompany.com/mcp",
      "headers": {
        "Authorization": "Bearer lac_sk_..."
      }
    }
  }
}

​

VS Code

{
  "servers": {
    "lac": {
      "type": "http",
      "url": "https://api.app.lastaccountingcompany.com/mcp",
      "headers": {
        "Authorization": "Bearer lac_sk_..."
      }
    }
  }
}

​

OpenAI API (Responses)

response = client.responses.create(
    model="gpt-5",
    tools=[{
        "type": "mcp",
        "server_label": "lac",
        "server_url": "https://api.app.lastaccountingcompany.com/mcp",
        "authorization": "lac_sk_...",
        "require_approval": "always"
    }],
    input="Which invoices are overdue, and by how much?"
)

​

Generic JSON

{
  "mcpServers": {
    "lac": {
      "type": "streamable-http",
      "url": "https://api.app.lastaccountingcompany.com/mcp",
      "headers": {
        "Authorization": "Bearer lac_sk_..."
      }
    }
  }
}

​

Tool reference

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Read tools (all keys)

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Write tools (write-scope keys)

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Security

• Use read-only keys for analysis agents. A key with read scope exposes only the 18 read tools — the agent physically cannot send an invoice or delete a document.
• Keep a human in the loop for destructive tools. send_invoice, create_credit_note, and delete_document are annotated destructive in the tool definitions; configure your client to require confirmation before calling them (most clients respect the annotation by default).
• Mind prompt injection when combining servers. If an agent has the LAC server alongside other MCP servers or web access, content fetched from elsewhere could try to steer it into calling LAC write tools. Prefer read-only keys in mixed-tool setups, and review write actions.
• Revoke instantly. Keys are revoked in the portal under Settings → API access; a revoked key loses MCP access immediately. OAuth connections end when you disconnect the connector in the client.
• API keys are company credentials, not personal ones — they keep working if the person who created them leaves. Revoke or rotate keys in Settings → API access when an admin departs.
• Tenant isolation and audit. Every tool call is scoped to the key’s company and audited, like every REST request.

​

What’s deliberately not exposed

• Payroll entirely (read and write) — payroll data and actions require an admin/approver in the portal UI.
• Company settings changes.
• Member and access management — inviting people, changing roles.
• API key management — a key can never mint or revoke keys.