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

Annotations already declare readOnlyHint=false and idempotentHint=true, so the mutation and idempotency profile is covered. The description adds genuinely valuable behavior beyond that: patch semantics (only supplied fields change) and the critical warning that `lines` replaces all line items rather than merging. What it omits is what happens when the document is not a draft.

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?

Two short sentences with no filler, and the partial-update rule plus the `lines` gotcha are front-loaded. Efficient, though arguably too terse given the tool's breadth.

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 25-parameter mutation tool with no output schema and low schema coverage, the description does far too little: it never states that the document must be a draft, never explains what is returned, and never covers interactions such as discount_percent vs per-line discounts or required-field implications when tax_regime changes.

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?

With 25 parameters at only 36% schema description coverage, the description must compensate, and it only does so for `lines` (replace-all semantics). The many undocumented fields (customer_name, payment_terms_days, service_date, closing_text, etc.) receive no guidance, though most are self-explanatory by name.

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 ("Einen Entwurf ändern" = modify a draft), which is clearly distinct from create_document, delete_draft, and finalize_document. It does not explicitly name those siblings, but the draft scope is unambiguous.

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?

The word "Entwurf" implies the tool applies only to drafts, which is a useful when-to-use signal, but it is never stated as a constraint nor contrasted with finalize_document or delete_draft. No prerequisites, no error conditions, no explicit alternatives.

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