billy_get_invoice

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

No annotations are provided, so the description carries full burden. It discloses READ-ONLY behavior but does not mention authentication requirements, error handling (e.g., missing id), rate limits, or response details beyond line items. For a get-by-id tool, this is insufficient for an agent to understand potential side effects or failure modes.

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 extremely concise: one sentence plus a tag. Every word adds value ('Fetch one invoice including line items' and 'READ-ONLY'). There is no redundancy or fluff.

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 simple get-by-id tool with only one parameter and no output schema, the description is mostly adequate: it explains the action and that line items are included. However, it does not describe what happens on success (e.g., returns full invoice object) or on error (e.g., not found). Given the absence of annotations and output schema, more detail would be beneficial for completeness.

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 has one required parameter 'id' with 0% description coverage. The tool description does not add any meaning to the 'id' parameter, such as format, source, or constraints. The description mentions 'including line items' but does not connect that to the parameter. For a single parameter, the description should clarify its purpose beyond what the schema provides.

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 'Fetch one invoice including line items', which specifies the verb (fetch), resource (one invoice), and scope (including line items). It distinguishes from siblings like billy_create_invoice (mutation) and billy_list_invoices (multiple invoices). The 'READ-ONLY' tag further clarifies it is a safe read operation.

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 reading a single invoice's details, mentioning line items. However, it does not explicitly state when not to use it (e.g., for listing multiple invoices) or provide alternatives. The 'READ-ONLY' tag gives some guidance, but lacking explicit exclusions or comparisons to siblings like billy_list_invoices or other get_* tools.

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