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

Annotations already declare this is a non-readonly, non-idempotent, open-world operation. The description adds concrete behavioral context beyond that: it logs in internally with the given credentials, redeems the voucher, removes the 'notactivated' role, and grants full access. That is valuable operational detail. It does not discuss failure modes or reversibility, keeping it from 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.

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

The first sentence is well front-loaded and states the core action. However, the description is bilingual, repeats the voucher-code concept several times, and includes some redundant German sentences. It is informative but not tight, so it earns a middle 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 mutation tool with three required parameters, annotations, and no output schema, the description covers the essential context: required credentials, code source, and the resulting account effect. It does not explain error behavior or return values, but the schema and annotations carry enough of that structural load. The description is therefore mostly complete.

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 all three parameters. The description reinforces the voucher as a 7-digit activation code from email and identifies the login fields as the registered account's email and password. This adds some clarity but is largely redundant with the schema, matching the baseline 3.

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?

The description clearly states a specific verb and resource: 'Activate a registered account with the voucher code.' An agent can understand the core action without opening the schema. It does not explicitly differentiate from nearby sibling tools such as register or redeem_invite_code, so it falls short of a 5.

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?

The description gives useful usage context: the code comes after email registration and can be obtained from a human or via IMAP. It also states that login credentials are required. However, it does not explicitly say when to use this tool instead of siblings like register, login, or redeem_invite_code, so guidance is implied rather than explicit.

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