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

Goes well beyond the annotations (readOnlyHint=false, destructiveHint=false) by disclosing that mailbox existence is NOT pre-checked, that a missing mailbox causes rejection with no change made ("das ist keine Störung"), and that only non-emptiness of target_address is validated while multiple recipients or display names are rejected later by Plesk. These are exactly the failure-mode details an agent needs and cannot get from structured fields.

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?

Three dense sentences, front-loaded with the core action and the required-parameter rule; every clause carries information (precondition, failure semantics, fallback tool). Slightly long and nested, but no filler.

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?

No output schema exists, and the description covers failure behavior, validation limits, and prerequisites well enough to call the tool correctly. It omits required permissions and any note on distinguishing enable vs disable side effects, which keeps it from a 5.

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 coverage is 100%, so a 3 is the baseline, but the description adds real semantics: target_address is required specifically when enabling (implying it is optional on disable) and may be an arbitrary external address. It largely echoes the schema's own notes about single-address format, so it stops short of a 5.

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 pair (enable/disable) applied to a precise resource (forwarding of an existing mailbox to an external address), and the parenthetical example ("leite info@ an meine private Gmail weiter") makes the operation unmistakable. It is clearly distinguishable from siblings like set_email_alias or create_email_account, which act on different resources.

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?

Explicitly gives the precondition (target_address mandatory when enabling) and routes the agent to an alternative: "Im Zweifel vorher get_email_accounts aufrufen, statt den Namen zu raten." It does not, however, contrast forwarding with the sibling set_email_alias, so the agent must infer that distinction.

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