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

Adds real value beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true): it discloses that nothing is sent to anyone, no confirmation prompt is required, the contact lands only in the user's own Kontakte list, and the API key needs app access. Slightly short of 5 since it doesn't address duplicate handling or the returned identifier.

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?

Purpose is front-loaded and each following sentence covers behavior, conditional params, or auth. There is minor redundancy in the 'sevdesk:' prefix and the 'like the Kontakt erstellen button does' analogy, but nothing is padded out.

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-param create tool with full schema coverage and no output schema, the description covers purpose, kind/name conditionals, side-effect scope, and auth. It could note how the created contact is identified in the response, but overall it is complete enough to call correctly.

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% so the baseline is 3, but the description consolidates the conditional requirement logic (kind + name for organization, first_name/last_name for person) and enumerates category values (Kunde, Lieferant, Partner, Interessent) beyond the schema's terse examples. Modest but genuine added meaning.

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 (add/create) and resource (contact/customer/supplier) and draws the person-vs-organization distinction up front. An agent can tell this is a creation tool for contacts without opening the schema, and it maps cleanly to siblings like sevdesk_list_contacts.

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 explains what kinds/categories exist and that the operation is private, which implies the create use case, but it never names an alternative (e.g. sevdesk_list_contacts) or states when not to use it. Usage context is implied rather than explicit.

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