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

Goes well beyond the annotations by disclosing that there is no dry run and the message is sent immediately, that push and email to agent addresses are deliberately suppressed, and the 4000-character limit. These are exactly the operational traits an agent needs before invoking a non-idempotent (idempotentHint=false) write.

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-loads the purpose, then parameter notes, then behavioral caveats, in a compact block. Some param detail (email, 4000 chars) duplicates the schema, and the trailing EN keyword list is filler, but overall it is tight.

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, yet the description covers delivery semantics, recipient constraints, size limit, and the read path. Nothing material an agent needs to call this correctly is missing.

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% and both params are self-documented, so the baseline is 3; the description adds value by stating the recipient must be an existing user and that the agent's own address is an acceptable target, which the schema does not convey.

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 (eine Notification schreiben / send) with the resource and scope (User-zu-User, handler 'user_message'). It explicitly separates this from the reading sibling by naming ontouser_notification_index, so an agent can distinguish them without opening schemas.

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?

Provides clear context: recipient must be an existing user, own address is allowed, and the reading counterpart is named. It doesn't state explicit when-not-to-use cases beyond the push/email exclusion, so it falls just short of full routing guidance.

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