update_invoice_line_itemsSet an invoice's line items — array of {description, amount} (dollars). Recomputes the invoice total. Replaces the whole list. Requires event_id + item_id; host.
| Name | Required | Description | Default |
|---|---|---|---|
| item_id | Yes | ||
| event_id | Yes | ||
| line_items | Yes |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations provide readOnlyHint=false, idempotentHint=true, destructiveHint=false. The description adds context by stating it recomputes totals and replaces the whole list, which goes beyond annotations. However, it does not detail permissions or reversibility.
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 front-load key information: verb, resource, data structure, effect, and requirements. No extraneous content.
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 tool with 3 required params and no output schema, the description covers the core behavior and parameter semantics. It could include more about error cases or permissions, but is sufficient given the idempotent 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 compensate. It explains that line_items is an array of {description, amount} in dollars and notes that the tool replaces the whole list, adding meaning beyond the schema's 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?
Description clearly states it sets invoice line items as an array of {description, amount}, replaces the whole list, and recomputes the total. This specific verb+resource distinguishes it from sibling tools like add_guest or update_event.
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?
Description mentions 'Replaces the whole list' and requires event_id, item_id, and host, providing some context. However, it does not explicitly state when to use this tool versus alternatives like updating individual items or using other update tools.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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