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

readOnlyHint=true already tells the agent this is a safe read; the description adds the AND-combination rule for filters and the pagination continuation mechanic, which are real behavioral facts. However, the pagination note largely restates what the page parameter's own description already says, and nothing is said about result volume, ordering, or what 'included' resources look like.

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?

Three short sentences, front-loaded with the resource definition before the filter and paging rules. The trailing 'GET /main/InvoiceLine' is low-value for an agent but harmless and short.

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 100% parameter coverage, zero required params, and a readOnly annotation, the agent has nearly everything needed. The remaining gap is small: no output schema and no mention of the response shape (e.g., that related resources land in an 'included' array when the include param is used).

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 all 13 parameters are already documented (prefix operators for amount/created/last_updated, comma-separated ids, enum for include). The description adds only the cross-parameter AND semantics, which is genuine but minor value over the schema baseline.

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 and resource ('List or search invoice lines') and even defines the resource as 'single fees on invoices'. It implicitly distinguishes itself from the getter sibling (halaxy_get_invoice_line) and from halaxy_list_invoices, but never names either alternative 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?

'Filters combine with AND' and 'Paged: pass next_page as page' give operational context, but there is no statement of when to prefer this over halaxy_get_invoice_line for a known id or halaxy_list_invoices for invoice-level data. Usage is implied rather than guided.

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