goal_seek
Determine the input cell value that drives a target output to a desired number. Runs a bisection search without modifying the workbook, returning the solution or a clear non-answer.
Instructions
Find the input value that makes a chosen output equal a target — "what discount rate gives a value per share of 30".
Runs entirely on the engine's temp branch, so the workbook is never modified: this is a question, not an edit. The search happens inside the engine rather than as a conversation, so it costs one tool call instead of one per iteration.
Name both cells semantically as (block, row_key, field) or by coordinate as (row, col). Give between when you know a bracket; otherwise it expands outward from the current input value to find one.
Bisection, so it needs the output to move monotonically between the bracket ends and it finds one crossing. If the bracket does not straddle the target it says so rather than returning a number — a non-answer you can act on beats a plausible one you cannot.
Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| to | Yes | The value `target` should reach. | |
| set | Yes | The input cell to vary. | |
| target | Yes | The output cell to drive to `to`. | |
| between | No | Search bracket [low, high]. Omit to expand outward from the current input value. | |
| tolerance | No | How close to `to` counts as solved. Default 1e-6 relative. | |
| max_iterations | No |