MainBook MCP¶

Local bookkeeping-conversion server (stdio, API key) - MainBook scopes itself to one job and does it well: converting PDF bank statements into checked JSON, Excel, or CSV with balance validation. It runs locally with a MainBook API key, talks to api.mainbook.ai for the conversion engine, and refuses to touch anything outside the folders the operator names.

Server type: Local (stdio via uvx or pip)
Auth: Account API key (MAINBOOK_API_KEY, mb_live_...)
Endpoint: api.mainbook.ai (REST under the local server)
Tools: convert_bank_statement, get_conversion, list_conversions, get_balance, output_folder
Pricing: 1 PDF page = 1 credit; 20-page signup grant; packages bought in the web app
Category: Finance / Accounting
Built by: mainbook.ai

Why This Matters for Operators¶

Bank statements are the worst part of bookkeeping: every bank exports differently, PDFs resist parsing, and a wrong number poisons reconciliation. MainBook turns the chore into one tool call - "convert ~/Downloads/march-statement.pdf and save the Excel next to it" - and returns 63 transactions with opening and closing totals reconciled against the statement. If the totals do not match, nothing is silently accepted; the validation flags it.

The boundary design is the trust story: the server can only read and write inside the folders passed as arguments or set in MAINBOOK_ALLOWED_DIRS, and it has no tool for buying credits, handling payments, or deleting anything. It cannot spend money it was not given.

Tools & Capabilities¶

Tool	Purpose
`convert_bank_statement`	Upload one PDF, run a conversion job, poll 30-900s, return reviewed JSON or write XLSX/CSV to disk
`get_conversion`	Pick up a job after a client timeout, write results to a chosen destination
`list_conversions`	Cursor-paged account job history
`get_balance`	Total, reserved, and available page credits
`output_folder`	Read or change the default local result folder

Operating limits: 500 pages and 50MB per PDF, 6 in-flight jobs per key, 90-day document retention. A client timeout does not kill the job - get_conversion picks it up by job ID.

Installation¶

{
  "mcpServers": {
    "mainbook": {
      "command": "uvx",
      "args": ["mainbook-mcp", "~/Downloads", "~/Desktop", "~/Documents"],
      "env": { "MAINBOOK_API_KEY": "mb_live_…" }
    }
  }
}

Requires Python 3.11+ (or pip install mainbook-mcp). Folder boundary via the args list or MAINBOOK_ALLOWED_DIRS (colon-separated on macOS/Linux, semicolon on Windows). The account must accept the API Terms or calls fail with api_terms_not_accepted.

Business Relevance¶

Bookkeepers convert statement PDFs into spreadsheets with reconciliation checks in one prompt
Finance teams keep bank data out of the agent context until it is structured and validated
Ops automation can route statement folders through the agent on a schedule, with the folder boundary as the guardrail
Audit prep gains checked CSV/JSON exports instead of hand-typed entries

Integration with CorpusIQ¶

MainBook is the intake step for the accounting layer CorpusIQ already connects: converted statements become clean CSV/JSON that feeds QuickBooks imports or CorpusIQ's financial connectors for reconciliation against live balances. The split of labor is clean - MainBook turns the PDF into checked data, CorpusIQ turns that data into cross-source financial truth.

Limitations¶

One job only - no general accounting, invoicing, or categorization tools
Page-credit pricing; heavy monthly conversion volumes need a package check
Local stdio means the folder boundary is only as strong as the operator's configuration
New listing - the MCP surface has no community track record yet