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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false and openWorldHint=true, so mutation and non-idempotency are covered structurally. The description adds genuinely new context: no notification is dispatched to the contact, and the call consumes API credits (10 per create vs 50 per invoice) against a limited monthly quota — a real cost constraint an agent must know before retrying.

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?

Three short sentences, front-loaded with the WRITE tag and the core operation before the cost note. Efficient, though the parenthetical credit/quota detail is slightly dense and could be trimmed without losing the key warning.

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 10-parameter creation tool with full schema coverage, no output schema, and annotations carrying the safety profile, the description covers operation, side effects and rate-limit/cost behavior. It stops short of saying what is returned (e.g. the new person id), which an agent would want after a create.

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% and all 10 fields (company_id, first_name, last_name, email, phone, etc.) are documented in the schema itself. The description adds no field-level semantics beyond that, so baseline 3 applies.

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 opens with an explicit operation tag ("WRITE") and a precise verb+resource: "add a contact person to an existing company." The scope qualifier ("to an existing company") separates it cleanly from list_persons / get_person and from the other create_* siblings, which target different resources.

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?

It implies the precondition that the company must already exist, and "Nothing is sent to the person" tells the agent this is a silent record creation. However, it names no alternatives (e.g. use papierkram_create_company when the company itself doesn't exist yet) and gives no explicit when-not guidance.

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