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

Annotations already declare readOnlyHint=true, so the safety profile is covered. The description adds substantive context beyond that: ordering (oldest first), the relationship to amount_paid, the imported-invoice empty case, and the return field set. It doesn't cover error behavior for an unknown invoice_id, keeping it at 4.

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?

Front-loaded with the core definition, then the disambiguating note about amount_paid, then the empty case and return shape. Every sentence carries information; the amount_paid sentence is slightly convoluted but earns its place as a disambiguator.

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 no output schema, the description does the right work by enumerating the returned fields and ordering, plus the imported-invoice edge case. It lacks any statement on error handling or volume/limits, which is a modest gap for a single-param read.

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 coverage is 0% with one required integer invoice_id, so the description must carry the load. It only implies the parameter ("one invoice") and never says where the id comes from (e.g. list_invoices or get_invoice) or what happens with an invalid id, so it adds minimal meaning over the bare schema.

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 resource — the individual payments recorded against one invoice — and its scope/ordering, which implicitly separates it from get_invoice (which gives the aggregate) and record_payment (which writes one). An agent can tell exactly what it gets back without opening the schema.

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?

Gives a clear context for use (you want the breakdown behind amount_paid) and a valuable exclusion: imported invoices have no payment history. It does not name a sibling alternative such as get_invoice, so it falls short of explicit when/when-not routing.

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