Sign invoice electronically

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 test mode behavior, optional mailing, error condition (046), and merging of files. It lacks details on return values or side effects, but overall provides substantial behavioral context.

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 two sentences, front-loaded with the core action and optional behavior, followed by a crucial prerequisite. No wasted words.

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 complexity (5 parameters, nested objects, no output schema), the description covers the main purpose and a key error. However, it does not clarify how files and inlineFiles interact (e.g., can both be provided?), nor what the tool returns (e.g., order number). More detail would improve 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?

Schema description coverage is 100%, but the tool description adds meaning beyond the schema by mentioning the external service name (PixelLetter), action 4, and the optional mailing behavior which relates to the notification parameter. This extra context helps the agent understand the tool's integration.

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 the tool sends documents to the PixelLetter invoice signing service (action 4) and optionally mails the signed PDF. This distinguishes it from sibling tools like send_letter and send_fax which are for physical sending, and get_account_info which is informational.

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?

No explicit guidance on when to use this tool versus alternatives. The description mentions a prerequisite (electronic signatures enabled) and an error condition, but does not compare to siblings or specify contexts for use.

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