Download invoice PDF

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

Annotations already declare readOnlyHint=true, so the read-only nature is known. The description adds further detail about return format (path or base64) and the ability to force one via 'as' parameter, which goes beyond what annotations provide.

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 with about four sentences covering purpose, usage, return format, and alternative tool. It is front-loaded with the primary action. Could be slightly more structured, but overall efficient.

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 tool has well-documented parameters (100% schema coverage) and no output schema, the description sufficiently describes the return types (path or base64) and the ability to force format. No missing critical information 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?

Schema covers all 4 parameters with descriptions, so baseline is 3. The description adds value by explaining the 'as' parameter's purpose and default behavior, and implies usage of other parameters (e.g., invoice number), elevating it above baseline.

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 uses specific verb 'Fetch' and clearly identifies the resource as 'PDF of an already-issued invoice'. It distinguishes the tool from its sibling 'send_document_email' by stating its purpose for when the user wants the document itself.

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 explicitly states when to use: 'for when the user wants the document itself'. It also provides an exclusion criterion: 'to send the invoice to the client by email, use send_document_email instead'. This clearly guides the agent on tool selection.

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