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

Annotations only give readOnlyHint=false, destructiveHint=false, openWorldHint=true. The description goes well beyond: validation happens before any preparation or change, the error message enumerates the allowable versions, and the applied value is read back from Plesk with an explicit admission when read-back fails instead of echoing the requested value. That is substantive mutation-behavior disclosure.

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

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

Front-loaded with purpose, then prerequisite, then failure/verification behavior. Dense but every sentence carries distinct operational information; slight length keeps it from a perfect score.

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

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

For a two-parameter mutation with no output schema, the description covers the prerequisite lookup, pre-change validation, error content, and post-change verification. Nothing an agent needs to call it safely is missing.

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

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

Schema description coverage is 100%, so the schema already documents both parameters, including the exact "X.Y" format and rejected examples. The description adds only a restatement of the example value and a pointer to get_php_versions; baseline 3 applies when the schema carries the burden.

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

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

States a specific verb and resource ('Wechselt die PHP-Version einer Domain') and immediately scopes it against the sibling get_php_versions, which only reports available/current versions. An agent can distinguish the two without opening either schema.

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

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

Explicit routing rule: consult get_php_versions first, and NEVER guess a version. It also gives a concrete reason for the exclusion (the switch attempt may surface as a customer confirmation prompt), plus the precondition that unselectable versions are rejected up front.

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