add_invoice_entry

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

No annotations are provided, so the description carries the full burden. It does disclose key behaviors: the invoice must not be posted, tax behavior at posting time (multi-entry taxtables produce one split per entry), and how tax_included affects price interpretation. However, it doesn't fully describe what happens on error (e.g., if invoice is posted), what gets destroyed/reverted, or the exact return behavior. The tax timing disclosure is genuinely useful beyond schema.

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 well-organized with a clear header paragraph, precondition statement, and a labeled Args section mapping directly to the parameters. Somewhat long but every section adds value — no wasted words. The Args section mirrors the schema property names for easy cross-referencing.

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 9-parameter mutation tool with no annotations, 0% schema coverage, and no sibling clarification needed, this description is thorough. It explains all parameters with examples, discloses the posting and tax-timing behavior, and gives the GnuCash convention for the action field. No output schema is needed since the tool's behavior is self-explanatory in terms of what it mutates (adds a line). This is a complete description.

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 0%, so the description must compensate fully. It does: every parameter gets a detailed explanation including examples (invoice_id '000001', account 'Income:Sales', quantity '1'/'2.5', price '100.00'). It explains meaning beyond types for taxtable (tax components at posting), tax_included (gross vs pre-tax), notes (what doesn't belong on printed line), and action (GnuCash convention).

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 clearly states 'Add a line item to a customer invoice' with a specific verb (add) and resource (invoice entry). It distinguishes from siblings like add_bill_entry (bill vs invoice) and add_voucher_entry (voucher vs invoice). It also adds an important precondition ('The invoice must not be posted yet').

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 gives clear context on when to use this tool (adding line items to invoices, before posting), and the sibling names help distinguish from add_bill_entry for bills. However, it doesn't explicitly name alternative tools or state when NOT to use it (e.g., after posting), though 'must not be posted yet' implies that constraint. It doesn't mention when to use post_invoice vs this.

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