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

The annotations only provide destructiveHint: true, while the description adds 'MUTATES Quaderno data', the HTTP endpoint, and the return value ('Returns the created invoice incl. permalink, pdf'). This meaningfully goes beyond the annotation by describing the mutation's external effect and response, without contradicting it.

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?

The description is compact and front-loaded with the core mutation signal, then moves to required inputs, optional field routing, item structure, and return behavior. The long parenthetical list makes it a little dense, but every sentence contributes useful 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 create tool with no output schema, the description covers the essential call contract: required input relationship, optional attributes, item structure, endpoint, and return value. It does not discuss error conditions or what happens if a contact_id is invalid, but it is sufficient for an agent to invoke the tool correctly in the common case.

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?

Although schema description coverage is 100%, the description adds real value: it clarifies the either/or relationship between contact_id and a contact object passed via fields, enumerates the attributes that can go through fields, and provides an explicit line-item shape ({ description, quantity, unit_price, tax_1_name?, tax_1_rate?, discount_rate?, … }) that the schema leaves underspecified. This materially helps an agent construct valid parameters.

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?

The description names the exact action ('create an invoice') and resource ('Quaderno data', 'for a contact'), using a specific verb that separates it from sibling tools like list_invoices, create_contact, and create_transaction. It also states the API endpoint (POST /invoices), further pinning down what the tool does.

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 clear invocation guidance: provide contact_id (or a contact via fields) and items, and use fields for any other attribute. It does not explicitly explain when to prefer create_invoice over create_transaction or when not to use it, so it misses the strongest form of alternative routing, but the usage context is clear enough for correct selection.

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