bilig

Agent Spreadsheet Tool Call Loop

This page is for people building coding agents or backend workers that need a spreadsheet engine but do not want to drive a spreadsheet UI.

@bilig/headless lets the agent expose workbook operations as ordinary Node tools: read a range, set a cell, recalculate formulas, verify the result, and serialize the workbook for persistence. The important part is the loop, not the agent framework around it.

Runnable Example

Run the maintained example from a clean checkout:

cd examples/headless-workpaper
npm install
npm run agent:tool-call

The example builds a workbook with Inputs and Summary sheets, then executes one agent-style tool call:

{
  "toolName": "setInputCell",
  "arguments": {
    "sheetName": "Inputs",
    "address": "B3",
    "value": 0.4,
    "reason": "Use the latest qualified pipeline conversion estimate."
  }
}

The tool result reports the edited cell, before and after formula outputs, restored workbook outputs, and persistence checks. A passing run proves that:

• the write targeted Inputs!B3
• Expected ARR moved from 60000 to 96000
• Target gap moved from -34000 to 5600
• formulas persisted after serialize and restore
• restored values matched the post-write values

That is the contract an agent needs. It should not have to infer formula success from a screenshot.

Tool Shape

Keep the first tool surface small:

• readRange(range) returns computed values and serialized cell contents.
• setInputCell({ sheetName, address, value, reason }) validates the sheet and A1 address before writing.
• every mutating tool returns before and after computed values.
• persistence happens only after the verification readback succeeds.

This shape works with OpenAI tool calls, local coding-agent tools, queue workers, and normal service endpoints because the WorkPaper API is the boundary. The agent SDK can change without rewriting the workbook logic.

Files To Inspect

• runnable script: examples/headless-workpaper/agent-tool-call-loop.mjs
• external smoke check: scripts/workpaper-external-smoke.ts
• package contract: packages/headless/README.md
• longer recipe: docs/agent-workpaper-tool-calling-recipe.md

When This Is A Good Fit

Use this pattern when a product asks an agent to edit a forecast, refresh a scenario, check a formula-backed model, or generate a workbook artifact from service data. Keep the model responsible for choosing the next action, and keep the WorkPaper tool responsible for addresses, formulas, recalculation, and persistence proof.

If the workflow needs HTTP boundaries instead of direct function calls, start with the Node service recipe. If the input is JSON records rather than arrays, use the json-records-input.mjs example.

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