Horizon MCP Server

rdsh_farm_action

DestructiveIdempotent

Enable or disable RDS farms by safely draining new sessions before maintenance. Fetches each farm's full state, toggles enabled, and updates it.

Instructions

Enable or disable one or more RDS farms.

Disabling a farm prevents new sessions from being routed to it without terminating existing sessions — useful for draining a farm before maintenance.

Unlike desktop pools, farms have no bulk enable/disable endpoint, and Horizon's farm update schema requires several fields beyond "enabled" (verified live — a naive partial-body PUT gets rejected). So this fetches each farm's full current state first, changes only "enabled", and PUTs the complete spec back — a real get-then- update round trip, not a guess. Reports per-farm results if any still fail.

Input Schema

TableJSON Schema

Name	Required	Description
`action`	Yes	enable: allow new sessions to this farm. disable: prevent new sessions (existing sessions continue until they end).
`confirm`	No	Only used when the server runs with HORIZON_CONFIRMATION=flag (clients without elicitation). Otherwise the user is asked to confirm directly in the client.
`farm_ids`	Yes	List of RDS farm IDs to act on

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv0.2.0Sep 30, 2026

addedInput schema / properties / confirm

Added value: +{
+  "default": false,
+  "description": "Only used when the server runs with HORIZON_CONFIRMATION=flag (clients without elicitation). Otherwise the user is asked to confirm directly in the client.",
+  "type": "boolean"
+}

First observedv0.1.0Sep 10, 2026

TDQS

A4.4/5.0

Behavior5/5

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

Adds substantial behavior beyond annotations: disable does not terminate existing sessions, there is no bulk endpoint, Horizon's farm update schema rejects partial bodies, so it does a real get-then-update round trip, and it reports per-farm failures. Annotations already flag destructive/idempotent, and the description enriches rather than repeats them.

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?

Front-loads the core action then layers rationale. Most sentences earn their place, though the 'verified live — a naive partial-body PUT gets rejected' aside is slightly editorial for a tool description.

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?

An output schema exists so returns need not be explained, and the description still notes per-farm result reporting. For a mutation tool with full annotations and complete schema, everything an agent needs to call it correctly is present.

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 coverage is 100%, so all three parameters (action enum, farm_ids, confirm) are already documented in the schema. The description reinforces the action semantics but adds no new syntax or format detail beyond the structured fields, matching the baseline 3.

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 (enable/disable) and resource (RDS farms) with scope (one or more). It is clearly distinguishable from siblings like update_rdsh_farm (spec editing) and desktop_pool_action (different resource).

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

Usage Guidelines4/5

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

Gives a concrete use case — draining a farm before maintenance — and contrasts with desktop pools which have a bulk endpoint. It does not explicitly say when to prefer this over update_rdsh_farm, so it stops short of full alternative-routing.

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

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