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

With no annotations, the description carries the behavioral burden. It discloses the mutual exclusivity of contactId/companyId and the persistent side effect that future invoices automatically adopt currency and terms. This goes beyond what the schema alone reveals, though it does not cover error behavior, idempotency, or return values.

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 two sentences with no filler. The most critical constraint is front-loaded, and the behavioral consequence is stated efficiently in the second sentence.

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?

The description captures the core intent, the cardinality constraint, and the automatic effect on invoices, which is enough for basic use. But with eight parameters, no annotations, no output schema, and no guidance on defaults or lookup requirements, the context is not fully complete.

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 only 38%, and the description compensates partially by clarifying that contactId and companyId are mutually exclusive and that currency/payment terms have ongoing effects. However, it does not add meaningful semantics for several parameters like notes, taxId, or billingAddress.

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 clearly states the action ('attach invoicing details'), the resource affected ('contact or company'), and a key constraint ('exactly one of contactId or companyId'). However, it does not differentiate itself from the near-identically named sibling 'billing_profile_create', so it falls short of full clarity.

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 description provides no explicit guidance on when to choose this tool over alternatives. There is a confusing sibling named 'billing_profile_create' that is never mentioned or contrasted, and no exclusions or preferred contexts are stated.

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