bilig

FastMCP Client for WorkPaper Formula Tools

Use this when a Python agent stack already uses FastMCP and needs workbook formula tools without opening Excel, LibreOffice, Google Sheets, or browser UI automation.

FastMCP owns the MCP client session. Bilig owns the WorkPaper formula tools: read sheets, read cells, write one input, verify recalculated readback, and export a WorkPaper JSON boundary.

Run The Client

cd examples/fastmcp-workpaper-client
uv run --python 3.12 --with 'fastmcp-slim[client]' \
  python fastmcp_workpaper_client.py --output .tmp/fastmcp-workpaper-proof.json

The script connects to:

https://bilig.proompteng.ai/mcp

The client code uses FastMCP directly:

from fastmcp import Client

It verifies the hosted Bilig MCP endpoint exposes:

• list_sheets
• read_range
• read_cell
• set_cell_contents
• get_cell_display_value
• export_workpaper_document
• validate_formula

Then it reads Summary!B2 and Summary!B3, writes Inputs!B3 = 0.4, checks the request-local restore proof, exports the WorkPaper document, and prints a compact JSON proof with verified: true.

Proof Shape

{
  "client": "fastmcp",
  "transport": "streamable-http",
  "endpoint": "https://bilig.proompteng.ai/mcp",
  "readback": {
    "expectedCustomersCell": "Summary!B2",
    "expectedCustomersFormula": "=Inputs!B2*Inputs!B3",
    "expectedArrCell": "Summary!B3",
    "expectedArrFormula": "=B2*Inputs!B4",
    "editedCell": "Inputs!B3",
    "previousSerialized": 0.25,
    "newSerialized": 0.4,
    "restoredMatchesAfter": true,
    "persisted": false
  },
  "verified": true
}

Hosted Endpoint Boundary

The hosted endpoint is stateless. It is useful for FastMCP tool discovery, smoke tests, and docs examples because it does not write user files.

Do not expect a later read_cell call against the hosted endpoint to observe a previous call’s edit. The set_cell_contents call returns request-local proof for that call. Use the local file-backed stdio server when the workflow must persist a private WorkPaper JSON file:

npm exec --package @bilig/workpaper@latest -- \
  bilig-workpaper-mcp \
  --workpaper ./pricing.workpaper.json \
  --init-demo-workpaper \
  --writable

Why This Fits FastMCP

FastMCP’s Client gives Python code a deterministic way to connect to local or remote MCP servers, list tools, and call tools with structured results. Bilig supplies the workbook formula side of that boundary.

This is a good fit for:

• Python agent tests that need a known MCP server;
• workflow agents that need exact sheet/cell addresses;
• formula-backed quote, payout, budget, or import-validation checks;
• a clean smoke test before wiring a private file-backed WorkPaper server.

Official FastMCP references:

• FastMCP client docs: https://gofastmcp.com/clients/client
• FastMCP community showcase: https://gofastmcp.com/community/showcase

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