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

readOnlyHint=true already covers the safety profile, and the description adds real behavioral context beyond that: the hard 3-month period ceiling, the chunking strategy, and the underlying endpoint POST /api/v2/getpurchorders. It does not mention pagination interplay with max_results or rate limits, but the key constraint is disclosed.

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 sentences, zero waste, and the constraint and chunking advice are front-loaded after the purpose. Nothing extraneous.

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?

For a read-only list tool with no output schema, the description usefully names the returned fields and notes that the reply reports the total row count. The main gap is that pagination behavior across max_results is not spelled out, but the essentials for correct invocation are present.

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 five parameters are already documented in the schema, and the description adds no syntax beyond the 3-month limit on period_start/period_end. The field list it provides describes the response, not the inputs. 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 and resource ('List purchase invoices (vendor bills)') and enumerates the returned fields (bill number, vendor, dates, totals, paid flag). This clearly separates it from merit_get_purchase_invoice (single invoice) and merit_list_sales_invoices (the sales-side sibling).

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 concrete operational guidance: the period may span at most 3 months and longer spans require several calls. It does not explicitly name alternatives (e.g. merit_get_purchase_invoice for a single bill, or merit_purchase_report for aggregates), so routing to siblings is left implicit.

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