whmcs_apply_creditApply credit to a customer's invoice by providing the invoice ID and credit amount, with an option to suppress notification emails.
Apply credit to an invoice
| Name | Required | Description | Default |
|---|---|---|---|
| amount | Yes | Amount of credit to apply | |
| noemail | No | Do not send email | |
| invoiceid | Yes | Invoice ID |
Changes observed during successful MCP inspections.
v1.2.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description should disclose behavioral traits. It merely states the action without detailing side effects (e.g., reduces invoice balance), authorization requirements, or whether the operation is reversible. The brevity leaves critical behavioral gaps.
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 a single, clear sentence with no extraneous information. It is appropriately sized and front-loaded for quick comprehension.
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?
Given no output schema and no annotations, the description should provide more context about return values, success/failure indicators, or prerequisites (e.g., invoice must have unpaid amount). The current text is insufficient for an agent to fully understand the tool's operation.
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?
The input schema has 100% coverage, explaining each parameter's basic role. The description adds no additional semantic detail beyond what the schema provides, so the baseline of 3 applies per the scoring guidelines.
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 'Apply credit to an invoice' clearly states the verb and resource, making the tool's purpose unmistakable. It is distinct from sibling tools like whmcs_add_payment or whmcs_update_invoice, which handle different operations.
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 provides no guidance on when to use this tool versus alternatives (e.g., whmcs_add_payment). The context signals and sibling list are available, but the description itself offers no usage context or exclusions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.