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

Annotations already declare this is a non-read-only, idempotent, non-destructive, closed-world write, so the description adds nothing on the safety axis. It omits behavior that actually matters for a settings mutation: whether unspecified fields are preserved or reset, whether the change applies immediately, and whether prior values are recoverable.

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?

One short, front-loaded sentence with no filler or redundancy. It is efficiently written; the weakness is underspecification rather than verbosity.

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 a mutation tool with five top-level parameters, a nested object, an enum, no output schema and no documented field meanings, the description is far too thin. An agent cannot tell what a call will change or what happens to settings it leaves out.

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?

Reported schema coverage is 0% at the top level; only the nested settings properties carry descriptions. The description never explains vat_number, company_number, job_reference_style (number vs prefixed) or job_reference_prefixes, nor how prefix values pair with the enum, so it fails to compensate for the coverage gap.

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 gives a verb ('Change') plus two broad areas it affects: how job references are read and how bills are entered in Xero. That is more than a restatement of the name, but 'how job references are read' is vague and the sentence never clarifies that it writes a stored settings object.

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?

There is no when-to-use guidance, no prerequisites (e.g. whether Xero must be connected first via connect_xero), no note about partial vs full updates, and no mention of any sibling alternative. The agent must infer everything from the title and schema.

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