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

With no annotations, the description must fully disclose behavior. It does explain that currency/terms set here become invoice defaults, but it does not clarify create-vs-upsert behavior, error handling for both/none of contactId/companyId, permissions, or side effects on existing profiles. This is a significant gap for a mutation tool.

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 core purpose and key constraint are front-loaded. It could be better structured with a bullet list for the constraint, but it is efficient and readable.

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 8-parameter create tool with no annotations and no output schema, this description is incomplete. It does not state the return value, conflict behavior, or how it differs from the similarly named billing_profiles_create. The mutual-exclusivity hint is valuable but not enough.

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 coverage is only 38%, so the description must compensate. It adds the essential constraint that exactly one of contactId/companyId is required and clarifies the downstream effect of currency and paymentTermsDays. However, it leaves notes, taxId, billingEmail, and billingAddress unexplained.

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 action ('Attach billing details') and a resource ('contact or company'), and adds the key mutual-exclusivity constraint. However, it does not differentiate from the nearly identically named sibling tool billing_profiles_create.

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?

Offers useful context about currency/terms defaulting to invoices, which implies a scenario for use, but does not explicitly state when to use this tool over billing_profiles_create, billing_profiles_update, or other alternatives. No when-not guidance is provided.

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