Retrieve a credit note

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

There are no annotations, so the description carries the full behavioral burden. It discloses the operation is read-only, describes what the return includes (TypeCredit, Reason, amounts, PDF URL), and explains the important edge case where naming a debit invoice causes the tool to say so rather than misrepresent it. This is substantial behavioral context for a simple retrieval tool.

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 dense but not padded. It front-loads the main purpose, then immediately covers return contents, read-only behavior, identifier usage, the endpoint edge case, and the sibling alternative. Every sentence contributes actionable 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?

With no output schema, the description appropriately enumerates key return elements and even notes where the PDF URL comes from. It covers identifier conflict, wrong-target behavior, and alternative routing. For a two-parameter read-only retrieval tool, nothing an agent needs to call it correctly 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?

The schema already describes both parameters at 100% coverage, so the baseline is 3. The description adds meaningful semantics beyond the schema by stating exactly which identifier concepts map to the parameters and by adding the mutual-exclusion rule: pass one, not both. That extra guidance justifies above-baseline scoring without reaching 5.

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 starts with a specific verb and resource: 'Retrieves one ProAbono credit note with all its detail.' It differentiates from get_invoice by explicitly noting that a debit invoice should be fetched with get_invoice, and it clarifies the credit-note-as-invoice relationship. An agent can immediately understand what this tool returns and how it differs from close siblings.

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 gives explicit selection guidance: use get_credit_note for credit notes and get_invoice for debit invoices. It also specifies identifier usage requirements: 'Identify it by internal identifier or by full number; pass one, not both.' This leaves no ambiguity about when and how to invoke the tool.

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