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

With no annotations provided, the description carries the full burden. It discloses the external side effect (email to a third party), the sending identity (user's own address), and failure modes (no email account/Resend connected, Groundbase won't send). It also warns about confirmation, making the tool's behavioral profile unusually transparent.

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 three sentences, each carrying necessary information: purpose, user-confirmation warning and draft caveat, and failure behavior. It front-loads the primary action and adds constraints without padding.

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?

The description covers the core action, prerequisites (issued invoice), warnings, and failure modes. It does not mention return values or idempotency, but for a send tool with only 3 parameters these are minor gaps. Overall it is reasonably complete, though it could state what a successful call returns.

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 coverage is 67% (to and sendVia have descriptions). The tool description does not add any parameter-specific meaning beyond the schema; it only references the customer as the default recipient, which the schema already states. Baseline of 3 is appropriate given the schema does the heavy lifting.

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 opens with a specific verb and resource: 'EMAIL an issued invoice to the customer, from the user's own email address.' It clearly distinguishes from related tools by specifying 'issued' and stating 'A draft cannot be sent because it has no number yet.' This leaves no ambiguity about what the tool does.

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 provides explicit usage guidance: confirm with the user before sending, never send to 'check it looks right', and notes drafts cannot be sent. It also explains when it fails. However, it does not explicitly name alternative tools like email_send or invoices_issue, so it offers clear context but not full sibling routing.

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