Receivables (who owes us)

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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety bar is largely met. The description goes beyond them by disclosing a real data limitation (the UOL API exposes no payment status for received/purchase invoices) and the default ordering (most overdue first), both of which affect how results may be interpreted. It does not discuss pagination or truncation behavior, though the schema's limit description partly covers that.

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 tight sentences, front-loaded with the resource and return shape before the usage questions and the scope caveat. The Czech term "pohledávky" is domain flavor that earns little for an agent, but it costs only a clause.

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 an output schema present, the definition needn't explain return values, and annotations cover the safety profile; the description supplies the remaining essentials — scope limits and default ordering. The main residual gap is guidance on when this beats search_sales_invoices for overlapping invoice-level queries.

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 high (78%) and enums are self-explanatory, so the schema carries most parameter meaning. The description only echoes the default sort ("most overdue first by default") and does not clarify interactions such as how state, overdue_only and the date ranges combine. That is baseline-level added value.

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 names a specific resource and result shape: "Receivables of issued (sales) invoices — totals per currency plus the matching invoices," plus a default ordering. It also bounds the resource (sales invoices only, no purchase-invoice payment status). It stops short of explicitly contrasting with the sibling search_sales_invoices, which an agent must still disambiguate on its own.

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?

Concrete triggering questions ("who owes me money", "what is overdue", "has customer X paid") give the agent clear contexts to reach for this tool, and the closing sentence is an explicit when-not for purchase invoices. There is no explicit routing to alternatives such as search_sales_invoices or get_financial_overview for the overlapping receivable-total case.

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