Record payment

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

The description adds substantial behavioral context beyond the annotations: it states this is a write operation with 'real accounting effect,' explains that it posts cash and reduces invoice balance, and explicitly warns 'Not idempotent, so a repeated call records a second payment.' It also clarifies the behavior of omitting invoice_id, producing an unapplied credit. This exceeds what annotations alone convey.

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 four sentences with no filler, front-loading the core action and then moving from usage timing to accounting effect to idempotency to invoice behavior. Every sentence adds a distinct, useful piece of information that helps an agent call the tool correctly.

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 mutation tool with one nested payment object, the description covers when to call it, what accounting side effects occur, the non-idempotent risk, and the key decision about invoice_id. The schema documents all parameters, and an output schema is present, so no necessary context 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 description coverage is 100%, so the baseline is 3. The description reinforces the invoice_id semantics already present in the schema ('Supplying invoice_id links the whole total_amount to that invoice; omitting it leaves an unapplied credit'), but it does not add new parameter-specific meaning beyond the schema. It appropriately relies on the schema for details like txn_date and total_amount constraints.

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 opens with a specific verb and resource: 'Record a payment received from a customer, optionally applied against a specific invoice.' This clearly identifies the tool's action and scope, and it distinguishes create_payment from sibling payment tools like update_payment, delete_payment, get_payment, and search_payments by focusing on recording a new payment.

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 explicit when-to-use guidance: 'Use it once the money has actually arrived, after confirming the invoice Id with get_invoice or search_invoices.' It names the exact prerequisite tools to use first and clarifies when an invoice should be supplied versus omitted. This is strong routing guidance with no ambiguity.

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