---
title: "tool si.act.weigh"
description: "a hypothesis, and a fact or a test's reading: the hypothesis with the evidence attached and its standing recomputed against its bar."
section: reference
address: /reference/tools/si-act-weigh
contract: 0476e35e6e275db5
---

# tool si.act.weigh

a hypothesis, and a fact or a test's reading: the hypothesis with the evidence attached and its standing recomputed against its bar.

[figure: Over MCP, si.act.weigh takes WeighInput and returns a card whose body is Hypothesis.]

the hypothesis with the evidence attached and its standing recomputed against its bar. The call needs the act grant at the strategy rung.



| | |
|---|---|
| input | [WeighInput](/concepts/weighinput) |
| result | a card whose body is [Hypothesis](/concepts/hypothesis) |
| read-only | no |
| destructive | yes |
| card address | `ui://scale-intelligence/cards/Hypothesis` |
| HTTP route | [`/v1/act/weigh`](/reference/act/weigh) |





| field | type | required | note |
|---|---|---|---|
| `hypothesis` | `id` | yes |  |
| `for` | [EvidenceRef](/concepts/evidenceref) | no |  |
| `against` | [EvidenceRef](/concepts/evidenceref) | no |  |