Sales and purchases summary

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

The annotations include readOnlyHint=true and openWorldHint=false, so the description doesn't need to explain that operations are read-only. The description adds critical context by explicitly stating that the summary is 'indicative only' and NOT the official VAT return, which is valuable for setting expectations. However, it doesn't disclose other behavioral traits like performance characteristics or whether it covers partial periods, which might be relevant. No contradiction with annotations.

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 description is concise, front-loaded with the core purpose, and includes a clear limitation. It does not waste words or restate the title. The structure is effective for quick comprehension.

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?

Given the tool has a simple output, no output schema, and readOnly annotation, the description covers the main purpose and an important limitation (not official VAT return). However, it leaves ambiguity about how to specify a custom period (via date_from/date_to) and what happens if neither month nor dates are provided. The tool is moderately complex with 3 optional parameters, and the description could be more explicit about parameter interactions and output contents.

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 only 33%, with only the 'month' parameter described. The description mentions 'month or period' but doesn't clarify how to specify a period (e.g., using date_from and date_to) or whether both are required together. It adds some context beyond the schema but doesn't fully compensate for the low coverage on the two date parameters.

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?

The description clearly states that the tool provides a summary of sales and purchases for a month or period, including counts, totals, VAT, and top customers/suppliers. It distinguishes itself from sibling tools like nula_search_invoices or nula_receivables_report by focusing on aggregation rather than individual records. However, it does not explicitly differentiate from potential summary siblings, but given the list, it stands out as the only summary tool.

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 description implies usage for monthly/period summaries but does not explicitly state when to use this over alternatives. It doesn't say 'use when you need aggregated totals' or direct the agent to other tools for detailed data. The mention of 'indicative only' hints at limitations but not at alternative tools. This leaves some inference to the agent.

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