the-real-hetzner-mcp

hcloud_create_volume

Create a Hetzner Cloud Volume, optionally attaching it to a server or placing it in a specified location for unattached storage.

Instructions

Create a Volume

Creates a new Volume attached to a Server. If you want to create a Volume that is not attached to a Server, you need to provide the location key instead of server. This can be either the ID or the name of the Location this Volume will be created in. Note that a Volume can be attached to a Server only in the same Location as the Volume itself.

Specifying the Server during Volume creation will automatically attach the Volume to that Server after it has been initialized. In that case, the next_actions key in the response is an array which contains a single attach_volume action.

The minimum Volume size is 10GB and the maximum size is 10TB (10240GB).

A volume’s name can consist of alphanumeric characters, dashes, underscores, and dots, but has to start and end with an alphanumeric character. The total length is limited to 64 characters. Volume names must be unique per Project.

Operation specific errors

Status	Code	Description
`422`	`no_space_left_in_location`	There is no volume space left in the given location

Input Schema

Name	Required	Description	Default
`body`	Yes
`wait`	No	Poll the resulting action until success/error or timeout.

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.2.0Oct 29, 2026

TDQS

A3.9/5.0

Behavior4/5

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

Annotations cover the safety profile (destructiveHint=false, openWorldHint=true), and the description adds real behavioral context beyond that: automatic attachment after initialization, the `next_actions` array containing a single `attach_volume` action, and the 422 `no_space_left_in_location` error. It omits the meaning of the `wait` polling parameter and whether creation is idempotent, keeping it short of a 5.

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?

Content is front-loaded with the core create-and-attach behavior, then constraints, then an error table; nearly every sentence carries information. Slightly verbose in the naming-rules paragraph, but no filler.

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

Completeness4/5

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

For a creation tool with no output schema, the description covers the attach semantics, the response's `next_actions` hint, size/name constraints, and a documented error case. The gaps are the polling semantics of `wait` and post-creation state, but nothing critical for a correct invocation is missing.

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 50%, and the description adds genuine value for `server` vs `location` (mutually substitutable, same-Location constraint) and for `size`/`name` (range, charset, uniqueness per Project). However, `format`, `automount`, and `labels` are left entirely to the schema, so it only partially compensates for the coverage gap.

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?

Specific verb + resource (create a Volume) with the key nuance that the Volume can be created attached to a Server or standalone in a Location. This implicitly distinguishes it from sibling hcloud_volume_attach_action, which attaches an already-existing Volume, though it never names that sibling explicitly.

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?

Explicitly states the condition that selects each mode: provide `server` to create-and-attach, or `location` instead for a detached Volume, plus the constraint that the Volume must be in the same Location as the Server. It gives hard limits (10GB–10TB) and naming rules, but does not route the agent to alternatives such as volume_attach_action or volume_resize_action.

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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