mercury_list_invoice_attachments

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

Annotations already indicate readOnlyHint=true. The description adds critical behavioral details: download URLs are short-lived requiring refetch before download, and it returns a specific structure. 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 (three sections: what, use when, do not use, returns) with no redundant sentences. Every sentence adds value.

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 a single parameter, no output schema, and annotations providing safety hints, the description is complete. It includes return format and critical usage notes, leaving no ambiguity for agent 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 with a description for invoiceId. The description adds no extra semantic value beyond what the schema provides, but the parameter is simple and well-documented; baseline 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 clearly states it lists attachments associated with an invoice, specifying types (PDF copies, supporting documents). The use case section further clarifies purpose, and it is distinct from sibling tools like mercury_get_invoice or mercury_create_invoice.

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?

Explicitly provides USE WHEN and DO NOT USE guidance, including alternatives (upload is not supported) and a note on short-lived download URLs. This helps the agent decide when to invoke and when not.

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