invoices_email

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

Goes well beyond the annotations: discloses asynchronous queue-based delivery, a Pro-plan gating rule for PDF attachments, and the exact rejection error EMAIL_RECIPIENT_NOT_CLIENT for non-client addresses. It does not cover duplicate/resend behavior or delivery failure handling, which matters for a non-idempotent send.

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?

Four short sentences, each carrying distinct information (what it does, prerequisite, async behavior, plan gating, recipient rule). The primary action is front-loaded and nothing is filler.

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 10-parameter mutation tool with no output schema, the description covers the operation, prerequisites, side-effect timing and failure modes well. It never indicates what the call returns (queue id, message id, status) nor points to invoices_email_history for verification, which are the remaining gaps.

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 100%, so the baseline is 3, but the description adds a constraint not present in the schema: to/cc/bcc must be client emails registered on the company. That is genuine semantic guidance for three parameters rather than restatement.

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?

States a specific verb and resource ('Send an invoice via email') plus the scope of what can be included (optional PDF and XML attachments). This distinguishes it cleanly from invoices_pdf, invoices_email_defaults, invoices_email_history and the parallel delivery_notes_email / proforma_invoices_send siblings.

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?

Gives an explicit prerequisite workflow ('Use invoices_email_defaults first to get pre-filled subject and body') and hard constraints on recipients. It stops short of naming when not to use it (e.g. share links or the proforma send path), so it is clear context without explicit exclusions.

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