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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered. The description adds one genuinely useful behavioral caveat (demo-only scope), but offers no further operational detail such as account prerequisites or pagination.

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 front-loaded single sentence plus a short scope note; nothing is wasted. The trailing 'Works on: Demo invoicing (sample data).' fragment is slightly detached from the main clause but earns its place as a constraint.

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?

With an output schema present and annotations covering the safety profile, the description only needs to convey purpose and scope, which it does. The remaining gap is the lack of sibling differentiation rather than missing behavioral essentials.

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% for the single 'account' parameter, including its fallback behavior when only one account is connected. The description adds no param-level meaning beyond the schema, so the baseline of 3 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?

The description names a specific resource set ('Document series and VAT rates') and adds scope ('set up in the invoicing account, and which series is used by default'). It is clear what the tool returns, though it overlaps with the sibling vat_list and invoices_list without distinguishing itself from them.

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?

Usage is only implied: the description notes it 'Works on: Demo invoicing (sample data)', giving a scope constraint, but it never states when to prefer this over vat_list or invoices_list, nor any exclusions. No alternatives are referenced.

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