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

Annotations already declare destructiveHint=true, so the safety profile is partly covered. The description adds a genuinely useful trait beyond the annotations — 'only the fields you pass are sent' (partial-update/PUT-with-merge semantics) — but says nothing about reversibility, side effects such as organisation-vs-person conversion, or required permissions.

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 tight clauses plus an endpoint reference, with the core semantics ('only the fields you pass are sent') front-loaded. Every element carries information and there is no filler.

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 12-parameter mutation the schema does most of the work and the partial-update behavior is covered, but the description omits consequences of the destructive update (e.g. whether omitted fields are cleared vs preserved is only partly answered) and any note on side effects or auth.

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%, so all 12 parameters are already documented in the schema, including the non-obvious ones (surename spelling, status codes, category ids). The description adds no parameter-level meaning beyond that, so the baseline of 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?

States a specific verb (update) and resource (contact), and clarifies the scope is 'an existing contact'. It does not name or distinguish itself from siblings like sevdesk_create_contact or sevdesk_get_contact, so the differentiation is only implied.

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 phrase 'existing contact' implicitly signals this is for modifications rather than creation, but there is no explicit when-to-use guidance, no mention of prerequisites, and no routing to alternatives such as sevdesk_create_contact for new records.

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