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

Annotations cover the safety profile (readOnlyHint=false, openWorldHint=true). The description adds substantial context beyond them: the exact returned status 'Przekazana do wysyłki', that the KSeF number appears only after Ministry of Finance acceptance, that the invoice becomes non-editable/non-deletable afterward, the issue-date constraint, and the per-call confirmation requirement. This is exactly the elaboration annotations cannot carry.

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?

Front-loads what the tool does, then layers prerequisites, consequences, and the return status. Dense with no obvious filler, though it is long and could be tightened slightly.

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 it is a mutation tool with openWorldHint, the description covers prerequisites, irreversible side effects, the immediate return value, how to obtain the eventual KSeF number, and authentication (Cotlet API key with app access). Nothing an agent needs to invoke it correctly appears 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 coverage is 100% (invoice_id documented as 'Invoice ID from list_invoices'), so baseline is 3. The description adds the constraint that the issue date must not be later than the sending date and clarifies what happens to the referenced invoice, slightly exceeding the schema's guidance.

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 (send), resource (one issued invoice), and target system (Polish KSeF e-invoicing). Distinguishes itself from siblings like ifirma_send_invoice_email and ifirma_book_ksef_purchase_invoice by naming the exact destination.

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?

Explicit when-to-use conditions: KSeF must already be connected in the account; the issue date cannot be later than the sending date. It also names the read-back alternative (get_invoice) for retrieving the KSeF number, and requires user confirmation before each call.

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