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

Annotations already declare destructiveHint=true, idempotentHint=false and readOnlyHint=false, so the danger profile is known. The description adds one genuine behavioral rule beyond that: the end date must not precede the rental start date. It does not state whether termination is reversible, effective immediately, or what happens to the contract record afterwards.

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 front-loaded sentence naming the action and its two operands with zero filler. It is arguably over-terse for a destructive mutation, but nothing is redundant or buried.

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 destructive, non-idempotent, 3-required-parameter mutation with no output schema and only 33% schema coverage, the description leaves important gaps: the semantics of `reason`, whether the termination is immediate or scheduled, possible failure modes, and what the caller receives back. The annotations carry the safety story, but the description does not fill the remaining operational gaps.

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 only 33% — just `id` ("Vertrags-ID") is documented. The description compensates partially by mapping "Enddatum" to ended_on and adding a validation constraint (not before Mietbeginn), but says nothing about `reason`: free text, allowed values, or whether it is stored or only logged.

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 in German: "Laufenden Vertrag beenden" (terminate a running contract), with the key inputs named (Enddatum, Grund). "Laufenden" scopes it to active contracts, implicitly distinguishing it from delete_contract_draft, but no sibling is named 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?

Usage is only implied through the adjective "laufenden": the tool applies to active (running) contracts, not drafts. There is no explicit when-to-use vs. alternatives such as cancel_invoice, revise_contract, or delete_contract_draft, and no stated preconditions (e.g. contract must be signed).

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