Vaultbeat MCP Server

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Log weight (replaces day)

log_weight_entry

Destructive

Logs the owner's weight in kilograms for a given date, overwriting same-day entries, encrypted end-to-end, with optional Apple Health sync.

Instructions

Log the owner's weight (kg) on their behalf (agent write, 2026-07-21).

weight_kg: kilograms (positive, ≤500). date: LOCAL calendar day "YYYY-MM-DD" (default = today). Same-day upsert-in-place semantics (dayID = "body-{dayStart.epoch}") — re-logging the same day overwrites. Encrypted end-to-end before it ever leaves this machine.

Written data always lands in Vaultbeat cloud + MCP (visible to get_metric series "weight_kg"). Whether it also reaches Apple Health depends on an iOS setting, OFF by default: the MCP tab → "Allow AI to update Apple Health" (app 1.2.8 and earlier: Settings → Data & AI). When it is on, weigh-ins logged here sync back into Apple Health on the next app sync.

⚠️ If the owner wants this number in the Apple Health app, tell them to turn that toggle ON — do NOT tell them to re-enter it by hand in the Vaultbeat weight card. Logging it in both places produces two entries for the same day from different sources and corrupts the trend line. (Before 2026-07-28 this docstring said propagation was impossible and instructed exactly that manual double-entry; the toggle shipped 2026-07-22.)

Input Schema

TableJSON Schema

Name	Required	Description	Default
`date`	No
`weight_kg`	Yes

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv0.9.1Oct 3, 2026
- addedInput schema / additionalProperties
```
Added value: +false
```
First observedv0.8.1Sep 23, 2026

TDQS

A4.9/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Goes well beyond annotations: it discloses upsert-in-place keying (dayID = body-{dayStart.epoch}), end-to-end encryption before data leaves the machine, the dual write destination (Vaultbeat cloud + MCP, conditionally Apple Health), and a corruption failure mode from double-entry. The 'overwrites' semantics align with destructiveHint=true and the replace-day title.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The actionable content is front-loaded (units, params, upsert semantics) before the propagation details. It loses a point for changelog-style asides — dated stamps like '(agent write, 2026-07-21)' and the parenthetical about the pre-2026-07-28 docstring — that document history rather than guide invocation.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a mutation tool with an output schema already present, nothing an agent needs is missing: constraints, date semantics, overwrite behavior, encryption, downstream destinations, and the Apple Health toggle dependency are all stated. Return-value details are correctly left to the output schema.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must carry the load and it does: `weight_kg` is constrained (positive, ≤500) and `date` is defined as a LOCAL calendar day in 'YYYY-MM-DD' with a stated default of today. Neither constraint appears anywhere in the schema itself.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource with units and actor: 'Log the owner's weight (kg) on their behalf'. It also distinguishes itself from the read path by naming the sibling surface (`get_metric` series "weight_kg") where the written data appears, so an agent can route write vs. read without opening schemas.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly covers when to use it (agent-side weigh-in logging), what happens on repeat calls ('re-logging the same day overwrites'), and the alternative interaction pattern to avoid ('do NOT tell them to re-enter it by hand in the Vaultbeat weight card'). It also names the prerequisite for Apple Health propagation and the exact UI path to enable it.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.