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

The description states 'Reads only', but the annotations declare readOnlyHint: false. This is a direct contradiction: the structured metadata says the tool is not read-only while the description claims it is. Per the rubric, this inconsistency forces a score of 1 and triggers the annotation_contradiction flag.

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?

A single dense sentence that front-loads the purpose and then lists useful return details and the sibling pointer. Though long, every clause earns its place; it could be broken into two sentences for readability, but it has no filler.

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?

There is no output schema, so the description carries the burden of explaining return values—and it does so thoroughly (lines, taxes, reason, credited invoice, notes). It also covers the input format and the relationship to credit_note_list, making the tool fully usable by an agent.

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 parameter is fully documented in the schema with the exact formats ('CN-2026-0001' and 'CN-DRAFT-2026-0001'). The description only repeats 'CN number or draft id' without adding new meaning, so it matches the baseline of 3 rather than exceeding it.

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 uses a specific verb ('Return') and identifies the exact resource ('one credit note by its CN number or draft id'), and then enumerates the returned contents (lines, totals, reason, invoice, notes). It also contrasts with the sibling credit_note_list, making the tool's unique role explicit.

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 explicitly says 'use credit_note_list for the ids', which is a clear when-not and alternative directive. This tells the agent that if it lacks an ID, it should first call the list tool, leaving no ambiguity about when to invoke this getter.

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