TrueNAS MCP

Update App

update_app

Modify an installed TrueNAS app's configuration by applying a JSON values payload, with a dry-run preview by default and an option to apply changes.

Instructions

Update an installed app's configuration.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "app_name": "<app_name>",
      "values": "<values>"
    },
    "name": "update_app"
  }
}

Input Schema

Name	Required	Description
`values`	Yes	JSON string of updated values/config for the app.
`dry_run`	No	Preview only (default True); set False to apply.
`app_name`	Yes	Installed app name.

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Oct 23, 2026

TDQS

C2.9/5.0

Behavior2/5

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

No annotations are provided, so the description carries the full behavioral burden, but it does not disclose that changes are preview-only by default (dry_run=true), what happens to unspecified settings, whether a restart is required, or what permissions are needed. For a mutation tool with zero annotation coverage, this is a significant gap.

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?

A single, front-loaded sentence with no wasted words. It is efficient, though its brevity contributes to the missing usage and behavioral context.

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

Completeness2/5

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

Although an output schema exists and parameter descriptions are complete, the definition omits critical behavioral context for a mutation tool with no annotations: the default dry-run behavior is only in the schema, and there is no mention of prerequisites or side effects.

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

Parameters3/5

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

Schema description coverage is 100%, so the schema already explains app_name, values, and the dry_run default. The description adds no meaning beyond that, which matches the baseline 3 when schema does the heavy lifting.

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

Purpose4/5

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

States a specific verb and resource ('Update an installed app's configuration'), which is distinguishable from install_app, delete_app, and even upgrade_app. However, it does not explicitly say how it differs from upgrade_app, so the sibling differentiation is left implicit.

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

Usage Guidelines2/5

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

There is no guidance on when to use this tool rather than upgrade_app or the start/stop siblings, and no stated prerequisites such as whether the app must be stopped first. The agent must infer usage from the name alone.

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