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

Annotations cover safety (readOnlyHint false, openWorldHint true, idempotentHint false), and the description adds genuinely new context: it needs an e-mail or a Heimster sign-in, activation begins only after a confirmation link, and unsubscribe is one click. What it doesn't state is duplicate-alert behavior or any throttling, which keeps 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?

A single compact sentence front-loads the trigger, then the effect and prerequisites. The parenthetical multilingual synonyms are slightly dense but serve a real trigger-matching purpose, so nothing is wasted.

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 an 8-parameter mutation tool with no output schema, the description supplies the essential operational facts: the notification behavior, the required contact/auth, and the confirmation-gated activation. The remaining gap is that five of eight parameters are undocumented in both schema and prose.

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 only 25% (just place and language are documented), so the description must carry more of the load. It names the filter dimensions ('place, type, rooms, price and area') but maps them loosely — 'type' is ambiguous between category and property_type — and adds no enum values, defaults, or unit guidance.

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 ('notified about new listings', 'e-mails new matching listings') with the filter dimensions it operates on. It implicitly distinguishes itself from one-shot siblings like search_listings by framing continuous notification, though it never names those siblings explicitly.

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?

'Use this when someone wants to be notified about new listings' gives a clear trigger condition, reinforced by the multilingual synonyms (Suchabo, Benachrichtigung, alerte, avviso) that tell the agent when user phrasing maps here. No explicit when-not or named alternative, so it stops short of a 5.

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