Pay Hostkey invoices in full or in part from the account credit balance; deducts the specified amount and requires confirmation to complete.
Pay an invoice in full or in part from the credit balance (whmcs/apply_credit). MONEY: deducts funds from the account.
| Name | Required | Description | Default |
|---|---|---|---|
| amount | Yes | Payment amount in account currency | |
| confirm | Yes | Must be true to run the operation. | |
| invoice_id | Yes | Invoice number |
Changes observed during successful MCP inspections.
v1.0.3Input schema / properties / amount / descriptionPrevious value: -"Сумма оплаты в валюте аккаунта"New value: +"Payment amount in account currency"Input schema / properties / invoice_id / descriptionPrevious value: -"Номер инвойса"New value: +"Invoice number"v1.0.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=false and openWorldHint=true, so the write nature is covered. The description adds meaningful context by warning 'MONEY: deducts funds from the account' and noting partial payments, though it omits prerequisites such as sufficient credit or irreversibility.
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 short sentences, front-loaded with the action and resource, followed by a compact financial warning. The parenthetical API path is minor but harmless, and every sentence adds value.
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 simple financial write tool with full schema coverage and annotations covering the read/write boundary, the description is adequate but incomplete. It does not address prerequisites (e.g., sufficient credit balance), error behavior, or when to choose this over sibling payment tools like mass_pay.
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 schema already documents all three parameters. The phrase 'in full or in part' adds a small amount of meaning to the amount parameter by clarifying partial payments are allowed, but it provides no syntax or additional parameter-level detail beyond the schema.
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 states a specific verb ('Pay'), resource ('invoice'), scope ('in full or in part'), and funding source ('credit balance'). It is clear enough to distinguish from payment-gateway siblings, but it does not explicitly name alternatives such as mass_pay or create_addfunds_invoice, so it falls short of full sibling differentiation.
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?
There is no explicit when-to-use or when-not-to-use guidance, nor any mention of alternative tools. The purpose implies the tool is for paying an invoice from credit, but that is tautological rather than actionable routing advice.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.