Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

With no annotations, the description carries the full burden. It discloses that no key is required and that cloud targets hosted merchants, but says nothing about reversibility, idempotency, what happens to the underlying order/payment, or error behavior for an already-completed session.

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 scope, with no filler. Every clause carries information.

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?

A mutation tool with no annotations, no output schema, and 0% schema description coverage needs more than two sentences. The identifier's meaning and the consequences of cancellation are missing.

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 0%, so both parameters are undocumented in the schema. The description partially compensates for cloud (hosted merchant) and the auth posture, but leaves id entirely undefined — whether it is a session ID, order ID, or checkout token is unstated.

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+resource ("Cancel a UCP checkout session"), which inherently distinguishes it from siblings like uxc_complete_checkout and uxc_create_checkout. It does not explicitly name alternatives, and "UCP" is unexplained jargon, so it falls short of a 5.

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?

"No key; pass cloud for a hosted merchant" gives a conditional hint for the cloud parameter and the auth posture, but there is no guidance on when to cancel versus completing or abandoning a session, and no prerequisites or state requirements are stated.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.