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

The description adds important behavior beyond the annotations: partial-update semantics ('Pass only what changes'), full replacement of lines, and the immutability of finalized notes. These are meaningful operational details not present in the sparse annotations.

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 tight and front-loaded: the action and scope appear in the first sentence, followed by two high-value behavioral notes. No filler or repetition of the schema.

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?

It covers the critical rules for correct use: draft-only, partial updates, line replacement, and refusal of finalized notes. The main gaps are the absence of return-value information (no output schema) and the undocumented reason_detail parameter, but these are minor against the overall clarity.

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?

The description lists most updatable fields and clarifies that only changed values need to be passed, which is valuable. However, schema description coverage is only 56%, and reason_detail is not described anywhere in the description or schema, while recipient and issue_date also lack semantic detail.

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 opens with a specific verb and resource ('Change a draft credit note') and enumerates the mutable fields, making the tool's job unmistakable. The draft-only scope clearly separates it from credit_note_finalize, credit_note_create, and credit_note_delete.

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 explicitly states the tool applies only to drafts and that finalized notes are immutable and refused, giving a clear when/when-not signal. It does not name the alternative tool for finalized notes, but the sibling context makes the intended use obvious.

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