record_purchaseAtomic expense + optional inventory item creation. ($0.10; API key required)
| Name | Required | Description | Default |
|---|---|---|---|
| date | No | ||
| name | Yes | ||
| amount | Yes | ||
| currency | No | ||
| request_id | No | Client idempotency key (retries return original result). | |
| idempotency_key | No | Alias for request_id. |
| Name | Required | Description | Default |
|---|---|---|---|
| message | No | ||
| expense_id | No | ||
| transaction | No | Expense/income transaction row. | |
| inventory_id | No |
Changes observed during successful MCP inspections.
Input schema / properties / idempotency_keyAdded value: +{
+ "description": "Alias for request_id.",
+ "type": "string"
+}Input schema / properties / request_idAdded value: +{
+ "description": "Client idempotency key (retries return original result).",
+ "type": "string"
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description adds the transactional guarantee ('Atomic'), the $0.10 cost, and the API key requirement, none of which are present in the annotations. It aligns with readOnlyHint=false by indicating a write effect and does not contradict the annotations.
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 compact and front-loaded: the functional effect comes first, followed by cost and auth requirements in parentheses. Every part earns its place and there is no filler.
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?
The presence of an output schema reduces the burden of describing return values, and required parameters are visible in the schema. However, the agent still has to infer when to use this tool relative to siblings and receives no help understanding the optional parameters, leaving clear gaps.
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 only 33%, and the description does not explain what name, amount, date, or currency mean or how they map to the expense/inventory fields. The description fails to compensate for the schema's low parameter documentation.
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 clearly states the operation as an expense record with optional inventory item creation, and the word 'Atomic' signals a single combined effect. It helps distinguish from siblings like log_expense and add_inventory_item, though it does not explicitly use the word 'purchase' in the description body.
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?
'Optional inventory item creation' implies the tool should be used when both an expense and an inventory item are needed, but it does not explicitly name alternatives like log_expense or add_inventory_item. The usage context is implied rather than clearly stated.
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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