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

With no annotations, the description carries the full burden and says nothing about consequences: whether the created document is finalized/immutable, whether the series counter is consumed, how client_id vs. client_name resolution behaves, or what is returned. A one-line 'Create X' is not enough for a mutation tool with zero annotation coverage.

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?

Single front-loaded sentence with zero redundancy — efficient. It is under-specified rather than padded, so the terseness cost is charged under completeness, not here.

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?

Eleven parameters, two required, no annotations, no output schema, and no explanation of the client identification fallback (client_id vs. client_name/city/address/country) or of defaulted fields (document_date, due_days, series, counter). The schema covers individual fields but the description offers no orienting context for constructing a valid document.

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% and the schema itself is rich (notably the discount_rate gating rules and the series default behavior), so the schema does the heavy lifting. The description adds nothing about parameters, which is the expected baseline of 3 when coverage is complete.

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?

A specific verb+resource: 'Create a new proforma invoice'. The qualifier 'for a client' implicitly separates it from create_supplier_proforma_invoice, but no sibling is named explicitly, and the distinction from create_invoice (proforma vs. fiscal) is left to inference.

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?

No statement of when to use a proforma instead of a real invoice, no prerequisites, no mention of what to do afterwards (e.g. send_document, submit to e-factura). The only hint is 'for a client', which is far too thin for an 11-parameter creation tool in a family of ~10 create_* siblings.

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