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

Annotations already declare readOnlyHint=false, openWorldHint=true, idempotentHint=false and destructiveHint=false, so the agent knows this mutates state and touches an external channel. The description adds genuinely useful context beyond that: the token arrives by email, the human must supply it (no mailbox access needed by the agent), and omitting it means the account expires. It stops short of describing failure behavior for an invalid or expired code.

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 the core action and largely free of filler; each clause carries distinct information (mechanism, cadence, trigger, actor, alternatives). The trailing '| EN: renew, account' fragment is redundant noise and the description repeats the schema's 'per E-Mail' detail, costing it the top mark.

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 single-parameter lifecycle tool with clear annotations and no output schema, the description covers everything needed to invoke it correctly: what triggers it, where the input comes from, the consequence of not calling it, and which sibling handles the adjacent cases. No output-schema explanation is required.

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 defines the single 'token' parameter as a 4-digit emailed verification token, which sets a baseline of 3. The description goes beyond that by specifying the operational source/actor ('Den Code besorgt der Mensch ... kein Postfachzugriff noetig'), telling the agent not to attempt email retrieval.

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+resource (Konto verlaengern) and immediately pins down the mechanism (4-stelliger Verifizierungscode) and the cadence (etwa alle 3 Monate). It explicitly fences itself off from the two nearest siblings: 'Zur Erstanmeldung: login' and 'Ein neues Konto entsteht hier nicht: dafuer register.'

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?

Gives an explicit trigger condition: 'Nutze es, wenn eine Verlaengerungsaufforderung kommt oder die Laufzeit auslaeuft.' It also names both alternatives (login, register) and the condition that selects each, so the agent needs no inference to choose among them.

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