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

Annotations already declare destructiveHint=true, idempotentHint=false and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: a hard state gate tied to schedule approval and the exact mechanism (accept_schedule_change applying an add_later_payment suggestion) that lifts it. It stops short of explaining what the mutation affects elsewhere in the schedule, which is where destructiveHint matters.

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 sentences, no filler. The payload definition comes first and the state constraint second, so the operation is front-loaded before the edge case.

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?

An output schema exists, so return values need no explanation, and the mutation's main non-obvious behavior (the post-approval refusal) is disclosed. What is missing is the scope of 'later payment' relative to the existing schedule (e.g., whether it affects recomputation or prior payments), which would explain the destructive hint.

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 carry the load, and it partially does: it clarifies that the amount is in whole minor units, which the bare 'amountMinor' integer does not. However 'payment date' is not tied to the dueOn field name or its YYYY-MM-DD pattern, and scheduleId is never mentioned, leaving ambiguity for an agent that must supply all four required parameters.

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 names a specific verb and resource ('Add one later payment') and enumerates the three payload pieces (label, amount, payment date), which map directly to required fields. It also distinguishes itself from add-type workflow siblings by naming accept_schedule_change as the path that must precede further additions.

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?

It gives a concrete usage condition: once the schedule is approved, direct additions are refused and accept_schedule_change (applying an add_later_payment suggestion) is the alternative. It doesn't say when to prefer this over suggest_schedule_change or move_payment_date, but the precondition and the named fallback are explicit.

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