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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety and reach profile is covered. The description adds 'No args — reads the platform catalog,' but that is largely a restatement of the empty schema and the readOnly hint, and it says nothing about catalog stability or size. Adequate but not additive.

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?

A single sentence with zero waste: the verb and payload come first, then the usage trigger and its rationale. Nothing is repeated or padded.

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?

With an output schema present, return values need no explanation, and the annotations cover the safety profile; the description supplies the pre-checkout context that is the only real complexity here. It is nearly complete, with the only omission being any disambiguation from the sibling list_catalog.

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 are no parameter semantics to document and the baseline is 4. The description's 'No args' note correctly reinforces the empty 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?

States a clear verb (List) and resource (the plan catalog), and enumerates the payload contents (tiers, intervals, product ids, prices), so an agent knows exactly what comes back. It does not differentiate itself from the similarly named sibling list_catalog, which is the one gap keeping this from 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?

Explicitly states when to call it ('BEFORE a checkout') and wires that to the concrete downstream consumer, create_checkout, explaining the consequence: requesting a real {plan, interval} instead of guessing an id. That is a named trigger plus a named alternative-to-avoid, exactly what this dimension asks for.

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