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

No annotations are provided, so the description must carry the behavioral burden. It does disclose a real side effect — a new supplier gets created automatically when address, city and country accompany supplier_name — which is the most valuable thing it could say. It says nothing about what happens on duplicate invoice numbers, what the call returns, or whether the document is only drafted versus finalized/submitted.

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 sentences, front-loaded with the core action, second sentence carrying the only branch that matters. Zero waste and no repetition.

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 an 11-parameter mutation with no annotations and no output schema, the description covers supplier resolution but not the response (does it return an ID? a document number?), nor prerequisites such as series selection or whether currency must match the supplier. The supplier branch is well handled; the rest of the call's contract is left to the schema.

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 11 parameters, including the nested line-item shape and the discount_rate gating logic, are already documented. The description's supplier_id priority and auto-create precondition largely restate the supplier_id and supplier_name schema descriptions rather than adding new semantics.

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 supplier invoice') and disambiguates the term with '(purchase invoice)'. It clearly separates from create_invoice (client invoice) by naming the supplier domain, though it never names create_simplified_supplier_invoice or create_supplier_order, so the sibling distinction is implicit rather than explicit.

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?

Gives concrete selection criteria for the two supplier paths: pass supplier_id when the supplier exists, or supplier_name + address fields to create it on the fly. It lacks any statement of when NOT to use this tool (e.g. versus the simplified/non-fiscal supplier invoice variants), which keeps it out of the top band.

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