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

Annotations only supply destructiveHint=true; the description goes well beyond that by disclosing NAV/Online Számla reporting, that the document can never be deleted but only reversed, that preview=true creates no document, and that the call is never retried. The warning that a returned invoice_number means a document WAS created is exactly the kind of side-effect detail an agent needs before re-issuing.

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-loaded with the most critical fact (fiscal, irreversible) and packs kind semantics, preview behavior, retry policy and email behavior into a tight paragraph with no filler sentences. The trailing 'Számla Agent action-xmlagentxmlfile' is internal plumbing that adds little for an agent and slightly dilutes an otherwise sharp block.

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 31-parameter fiscal mutation with no output schema, the description covers the irreversible-action risk, the preview mode, idempotency/lookup strategy and email side effects, and even hints at the reply shape. It stops short of describing the full response (PDF availability, error codes other than the e-invoice one), which an agent must infer.

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 already 100%, so the baseline is 3, but the description adds genuine semantics the schema does not: kind values are glossed (proforma = díjbekérő, non-fiscal, deletable; prepayment = előlegszámla), it states the tool computes net/VAT/gross from net_unit_price and vat_rate, and it explains what send_email_to_buyer actually does. It doesn't cover foreign-currency requirements despite the schema flagging them.

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?

Opens with a specific verb and resource ('ISSUES a real invoice in Számlázz.hu') and immediately differentiates itself from siblings by naming szamlazz_reverse_invoice and szamlazz_delete_proforma as the only ways to undo the variants. An agent knows exactly what this does and which tools are its counterparts without opening any schema.

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?

Explicitly routes between the three modes (invoice vs proforma vs prepayment) and names the sibling that handles deletion of a proforma. It also gives a clear operating rule for a failure case (never retried; look up via szamlazz_get_invoice by order_number or external_id) and tells the caller to always supply external_id/order_number so that lookup is possible.

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