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

Annotations only supply destructiveHint=true, so the description carries most of the burden. It adds real value by disclosing the return ('Returns the new id') and the price XOR rule, but says nothing about idempotency, duplicate-code behavior, error conditions, or what the destructive hint means for a create operation.

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, each earning its place: purpose, required inputs plus the key constraint, and the return value plus endpoint. Front-loaded with the action and free of 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?

With no output schema, the description correctly compensates by stating the return value ('the new id'). Combined with the required-field and XOR rules, an agent has enough to invoke it correctly; only failure/idempotency behavior is unaddressed.

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 schema already documents all 12 parameters including the price_excl/price_incl mutual exclusion. The description restates the required set and the XOR constraint, adding no syntax or format detail beyond what the schema provides, so the 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?

States a specific verb+resource ('Create a product or service') and names the endpoint (POST /v1/product), making it trivially distinguishable from siblings like create_invoice or create_relation. It also clarifies the tool covers services, not just physical products.

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 description gives preconditions (needs code, description, sale VAT code, ledger id, and exactly one of price_excl/price_incl), which is useful invocation guidance. However, it never states when to prefer this tool over an update path or what prerequisites (e.g. fetching a ledger id) must exist first, so usage context is only implied.

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