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

Beyond annotations (destructiveHint=true, idempotentHint=true), the description discloses that the operation releases an order draft, that completed/cancelled sessions are left unchanged, and that an idempotency-key is required in addition to ucp-agent. This is meaningful behavioral context, not a restatement of 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?

Three short sentences, each carrying distinct information: what the tool does, its state semantics, and its required metadata. The core action is front-loaded and there is no filler or repetition of the title.

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 mutation with an output schema and full parameter documentation, the description covers the main invocation needs: object to cancel, effect on drafts, idempotence, and required metadata. It could be more complete by explicitly routing to complete_checkout for finishing a checkout, but nothing essential for a correct call is 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 description coverage is 100%, so the baseline is 3. The tool-level mention of meta['idempotency-key'] is useful for emphasis but duplicates what the meta property description already states ('Obligatoria en complete_checkout y cancel_checkout'); the id parameter's source ('de create_checkout') is also already in the schema.

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 opens with a specific action and resource: 'Cancela una sesión de checkout UCP abierta', and adds a concrete effect ('libera cualquier borrador de pedido'). This clearly separates cancel_checkout from siblings like create_checkout, complete_checkout, get_checkout, and update_checkout.

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?

It states the applicable context—only an open checkout session should be cancelled—and that completed or cancelled sessions are unaffected ('Una sesión completada o cancelada no cambia'). It does not explicitly name alternatives or say when to use complete_checkout instead, so it stops short of full routing guidance.

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