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

Beyond annotations, it discloses that the invoice is only created and not sent, its status is unchanged, the user reviews it in smallinvoice, and calling twice creates two invoices. These are important workflow and duplication consequences that annotations alone would not convey as clearly.

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 WRITE marker and core action, followed by scope, endpoint, behavior, idempotency, and prerequisite lookup guidance. Every sentence adds useful information.

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 complex mutation with a rich schema and annotations, the description covers scope, side effects, non-idempotency, and prerequisite lookups well. It does not describe what the call returns, which is a minor gap given that no output schema is provided.

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 the schema already documents all seven required parameters in detail. The description only adds that list tools should be used to find contact and unit ids, without enriching the meaning of the remaining parameters beyond the schema.

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 ('creates a new invoice for a contact') and explicitly distinguishes creation from sending or status changes. An agent can tell this apart from sibling read/list tools such as smallinvoice_get_invoice or smallinvoice_list_invoices.

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?

It provides clear usage prerequisites: the 'invoice' scope is required, and contacts/units should be listed first to obtain ids. It does not explicitly state when not to use it or name a full alternative workflow, so it falls short of the top score.

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