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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), so the description's main contribution is disclosing the required OAuth scopes invoices.read and payments.read — genuinely useful auth context an agent cannot get from annotations. Paging behavior is left to the schema, which handles it thoroughly.

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?

Two short sentences, zero filler, with the resource and scope front-loaded before the permission requirement. Every clause carries information.

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?

A simple read-only list tool with full annotation coverage, a fully documented 3-parameter schema, and no output schema to explain. Adding a pointer to the alternative payment-search tool would make it complete, but nothing required for correct invocation is missing.

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 invoice_id, limit, and offset are already documented, including the non-trivial dual-mode offset contract. The description adds only the notion that invoice_id selects the parent invoice; baseline 3 applies when the schema does the heavy lifting.

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 (payments) with a clear scope qualifier: payments linked to ONE invoice. This is enough to distinguish it from the collection-wide sibling sellsy_search_payments, though it never names that sibling explicitly.

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 scoping phrase implies when to use it (per-invoice payment lookup), but there is no explicit when-not guidance or pointer to sellsy_search_payments for cross-invoice queries. Usage is inferable rather than stated.

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