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

Annotations already declare readOnlyHint/idempotentHint, so restating 'Read-only' earns little, but the description adds real operational context the annotations lack: required credential scope and the concrete 403 failure mode for sandbox keys from self-registration. It does not mention result limits or pagination behavior, which for a list tool is a remaining gap.

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, front-loaded with what is listed and what comes back before the prerequisite details. The 'Read-only' clause duplicates the annotation and is the one sentence that does not fully earn its place.

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?

There is no output schema, and the description compensates by naming the returned fields; auth and workspace-claim requirements are spelled out, including the 403 condition. Remaining ambiguity is around result volume/pagination, which is not addressed for a listing operation.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate and the baseline applies. The mention of returned fields (id, status, totals) adds orientation even though no inputs exist.

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 ('List') and resource ('UCP checkout sessions') scoped to 'your workspace', and enumerates the returned fields (id, status, totals). The plural/list framing makes it distinguishable from get_ucp_checkout and create_ucp_checkout without opening any schema.

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?

Gives clear preconditions for use: a Last Price credential with price compute scope, and a claimed workspace. It does not name an alternative tool or an explicit when-not-to-use condition (e.g. directing to get_ucp_checkout for a single session), 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.