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

Annotations already cover the safety profile (not read-only, not destructive, not idempotent), so the description earns credit for adding the defaults behavior instead: country NL, currency EUR, payment terms from business default — and the last two are leaked defaults not exposed as parameters at all. It does not warn that repeated calls can create duplicate clients despite idempotentHint=false.

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 action, then the hard requirements, then the defaults. Nothing is repeated and every clause carries information an agent needs.

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 non-destructive create with no output schema, the description covers action, required fields, and defaulted behavior. The remaining gap is the return value — whether the created client's identifier comes back, which matters for chaining into invoice creation.

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 already 86%, so the baseline is 3; the description goes beyond it by explaining why name and address are required (Dutch invoice law) and by disclosing currency and payment-terms defaults that appear nowhere in the schema. Optional fields like vatNumber and postalCode rely entirely on the schema, which is acceptable at this coverage.

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 ('Create a new client contact'), which cleanly separates it from the query-side siblings (lookup_contact, query_clients) without naming them explicitly. The domain rationale ('legally required on a Dutch invoice') sharpens what a client record is here.

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?

There is no explicit when-to-use / when-not guidance, no mention of checking for duplicates via lookup_contact, and no stated prerequisites or follow-on steps. Usage is only implied by the invoicing rationale, so an agent must infer that this belongs before create_invoice_draft/create_quote_draft.

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