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

Annotations only give readOnly=false / destructive=false / openWorld=true. The description adds real behavioral context: it creates the invoice document and the financial transaction, sending is irreversible ('cannot be taken back'), it reaches other people needing user confirmation, and it requires a Cotlet API key with app access. This is disclosure well beyond the structured fields.

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?

Purpose and channel options are front-loaded, and each sentence is meaningful. There is mild redundancy between 'you confirm each call' and 'confirm with the user before each call', but overall it stays focused.

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 an irreversible, open-world action tool with no output schema, the description covers the side effects (document + financial transaction), irreversibility, confirmation policy, and auth needs. Nothing essential for correct invocation is missing.

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%, so channel enum, division, invoice_id sourcing, and sender_email are already documented in the schema. The description repeats the channel list but adds no format or constraint detail beyond it, so the baseline 3 applies.

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+resource ('Send an existing sales invoice') and enumerates the delivery channels (email, postbox, Peppol). This clearly differentiates it from create_sales_invoice, get_sales_invoice, and list_sales_invoices in the sibling set.

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?

Establishes the precondition (an existing sales invoice) and the choice of channel, which gives an agent clear context. However, it never names an alternative tool (e.g., create_sales_invoice for invoices that don't exist yet) or states when NOT to send, so it stops short of explicit routing.

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