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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety is covered. The description adds genuine context beyond that: Xenition cannot send communications and the query is limited to the user's own ledger, which constrains expectations. It does not discuss result volume or pagination, keeping it below 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?

The core purpose is front-loaded in the first sentence, followed by filter behavior and then the usage constraints. Three sentences with no filler, though the exclusion sentence is somewhat long for the value it carries.

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 covering return values, annotations covering the safety profile, and 100% parameter coverage, the description only needs to supply purpose, usage, and boundaries — all of which it does. An agent has everything required to select and call it correctly.

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 both parameters (vendor, unpaidOnly) are already documented in the schema. The description restates the vendor and unpaid filtering in prose but adds no syntax or format detail beyond the schema, so the baseline 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?

States a specific verb (List) and resource (the user's own Xenition ledger invoices) with the paid/unpaid status dimension. It clearly delimits scope but differentiates by negative conditions rather than naming a sibling like add_ledger_entry or mark_paid, so it stops just short of the sibling-differentiation bar for a 5.

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?

Explicitly states when to use it ('asking to see or total invoices already recorded'), gives concrete examples ('what invoices are unpaid', 'how much do I owe vendor X'), and adds two clear when-NOT-to-use cases (sending/delivering invoices, and non-ledger invoices). Nothing is left to inference.

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