p2p_cancel_poCancel an order nothing has arrived against and no bill points at. With a reason. Once anything has arrived, the order cannot be cancelled: close the rest short instead. The order stays on the record as cancelled. Effects: order cancelled.
| Name | Required | Description | Default |
|---|---|---|---|
| po_id | Yes | The order. An existing p2p_po id. | |
| reason | Yes | Why it is cancelled. |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Goes beyond destructiveHint=true by explaining what destruction means here: the order is retained on record in a cancelled state rather than deleted. It also flags the blocking precondition. Gap: nothing about calling it twice or on an already-cancelled order, despite idempotentHint=false.
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?
Four short sentences, precondition front-loaded, alternative and post-state follow. 'Effects: order cancelled' is slightly redundant but harmless.
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?
No output schema and no annotations about reversibility, so the description carries that burden and does so for the pre-state and post-state. Missing only re-invocation behavior and any permission/authorization notes.
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 coverage is 100% and both parameters are documented in-schema. The description only adds 'With a reason', which is marginal value over the schema's own parameter descriptions.
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?
States a specific verb and resource ('cancel an order') plus the eligibility condition and required input. It differentiates from p2p_close_po_short by pointing to that alternative when goods have arrived.
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?
Explicit when-to-use (nothing received, no bill linked) and when-not (anything arrived), with the alternative route named ('close the rest short instead'). Preconditions and the fallback path are both stated.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Add one secure layer between your agents and this server.