External Invoices Update

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

Annotations already declare non-read-only, idempotent, non-destructive, open-world. The description adds genuinely new behavioral information: required OAuth scope (write_orders), the HTTP verb PUT (implying replacement semantics, consistent with idempotentHint), and the warning that the API version is unstable. It stops short of explaining what happens to invoice fields omitted from the payload under PUT.

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?

Four terse, front-loaded lines with zero filler — the warning, endpoint, scope and version are all immediately scannable. Slightly telegraphic rather than prose, but nothing is wasted.

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 7-parameter mutation with no output schema, the description covers auth and endpoint but leaves open whether this is a full replacement or a partial update (PUT vs merge, relevant to additional_fields) and what the response contains. Adequate but with meaningful gaps for a write operation.

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 every field (key, xml, number, series, issued_at, additional_fields) is already documented in the schema; baseline 3 applies. The description adds only the small detail that order_id and key are path parameters via the URL template, which is marginal added value.

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 ("Update an external invoice") and gives the exact endpoint, so the agent knows exactly what is being modified. It does not differentiate itself from the sibling external_invoices_create/get/list/delete tools or say why one would update rather than create.

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 guidance on when to use this versus tiendanube_external_invoices_create or the orders_invoices_* siblings, and no prerequisites beyond the scope string. The only contextual hint is the "unstable API" warning, which tells the agent to be careful but not when to choose this tool.

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