Update draft Wave invoice

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

Annotations cover the safety profile (readOnlyHint=false, destructiveHint=false, idempotentHint=false), so the bar is lower, yet the description still adds the important PATCH-style semantics (only passed fields change) and the notable exception that `items` replaces ALL line items, plus the draft-only refusal. It does not mention permissions/auth or currency side effects, keeping it short of a 5.

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?

Two tight sentences with zero filler, and the merge-vs-replace rule is front-loaded right after the draft-only constraint. Every clause carries operational meaning.

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?

An output schema exists so return values need not be explained, and the mutation's core behavior and precondition are covered. Missing only auth/permission expectations and what the caller should do when the draft-only guard rejects the call.

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 73%, so the schema already documents most parameters (including the items replacement note, currency default, and exchange_rate guidance). The description adds the update-merge semantics usefully but names no parameters beyond `items`, so the baseline 3 for schema-driven documentation applies.

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 verb (Change) and resource (DRAFT invoice) with an explicit scope restriction. It is immediately distinguishable from wave_create_invoice, wave_approve_invoice, and wave_send_invoice without opening any schema.

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?

Gives a clear precondition (only draft invoices; refuses non-drafts), which is the key gating condition for this tool. It stops short of routing the agent to a specific alternative for non-draft invoices (e.g., revert/approve flows) or pointing at wave_get_invoice for reads, so it is clear but not fully exclusionary.

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