create_invoice

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

With no annotations, the description carries the full burden. It usefully discloses that this is a mutating 'Add' operation and that ACUMULUS_TESTMODE=1 enables non-persisting validation, but it omits authentication needs, rate limits, and reversibility or failure behavior.

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 front-loaded with purpose and then structured under 'Args:' with parameter names. It is appropriately sized and each section earns its place, though it could be slightly tighter.

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 nested-object create tool with no annotations, the description covers the action, the main parameter shapes, and a dry-run option. An output schema exists, so return values need no explanation; remaining gaps like auth and sibling selection keep it from a 5.

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 0%, so the description must compensate, and it does: it documents common customer fields, line-item fields, defaults like vatrate=21 and quantity=1, unitprice format, and optional invoice-block fields. This adds substantial meaning beyond the empty schema property definitions.

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 gives a specific verb and resource: 'Add an invoice to Acumulus (invoices/invoice_add.php).' It is clearly distinct from generic siblings like whoami, acumulus_request, and list_picklist, even though it does not name alternatives.

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 only usage guidance is 'Set ACUMULUS_TESTMODE=1 to validate without persisting,' which is an operational option rather than a when-to-use statement. It does not explain when to prefer this tool over acumulus_request or describe prerequisites.

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