Record payment

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

Goes well past the annotations: no charge is made, no email is sent, the amount is capped at the amount due, full payment flips the invoice to paid, and payments sync to a connected accounting app (which explains openWorldHint). This tells the agent exactly what side effects to expect from a non-idempotent mutation.

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?

Two tight paragraphs: the first states the action and effect, the second supplies preconditions, limits and side effects. Every sentence carries information and the summary line is front-loaded.

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 no output schema, the description covers preconditions, amount constraints, downstream state changes and external sync. Combined with annotations that already declare safety and idempotency, an agent has everything needed to call it correctly.

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%, so all five parameters are already documented including defaults and the invoice_id provenance. The description echoes amount, date, method and reference without adding format or constraint detail beyond what the schema states, 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?

Names a specific verb and resource ('Record a payment received against an invoice') and states the resulting state change ('reduce the amount due'). No sibling tool touches payments, so the boundary is unambiguous from the sentence alone.

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 explicitly - the payment must already be received and the invoice must be approved - and clarifies scope with 'It charges nobody and emails nobody', which implicitly routes charging/notifying to tools like send_invoice. It does not name an alternative tool directly, so it stops short of a 5.

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