get_invoice

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

The description adds value beyond the readOnlyHint annotation by specifying that the response includes line items and payment status. It does not contradict annotations (readOnlyHint=true is consistent with retrieval). No negative or additional constraints are needed for this straightforward operation.

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 a single sentence that front-loads the verb ('Retrieves') and resource ('a specific invoice'). It is concise and contains no unnecessary information, earning its place with maximum efficiency.

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 simplicity of the tool (single required parameter, no output schema), the description adequately covers what the tool does and what the response includes (line items, payment status). It could mention that it returns the full invoice object, but the provided information is sufficient for selection and invocation.

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 input schema has 100% coverage on the single parameter 'id', with a clear description. The tool description does not add additional semantics about the parameter; it is already well-documented in the schema. Baseline score of 3 is appropriate.

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 states 'Retrieves a specific invoice, including line items and payment status,' which clearly identifies the action (retrieves), resource (specific invoice), and scope (includes line items and payment status). This distinguishes it from siblings like list_invoices (which retrieves multiple invoices) and update_customer_metadata (which updates).

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 implicitly indicates when to use this tool: when you need details of a single invoice by its ID. However, it does not explicitly mention when not to use it or suggest alternatives like list_invoices for multiple invoices. Nonetheless, for a simple retrieval tool, the context is clear.

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