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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, covering the safety profile. The description adds the exact return shape (`{ items: [{ grant, title, description, priceId, amountCents, scope }] }`), which is behavioral context beyond the annotations. It does not discuss errors or rate limits, but for a simple read-only listing this is sufficient. No contradiction with 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?

The description is two sentences, front-loaded with the core purpose and examples, then immediately provides usage guidance and the return format. Every sentence earns its place with zero redundancy.

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 tool with one optional parameter and no output schema, the description is complete: it states the purpose, gives usage context, lists the return structure, and provides examples. An agent has everything needed to decide when to call it and what to expect. No missing critical information.

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 schema description coverage is 100% (the single parameter `grant` has a description). The tool description does not add meaning beyond the schema for the parameter itself—it mentions examples of features but does not map them to enum values beyond what the schema says. The baseline of 3 is appropriate since the schema carries the parameter semantics.

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 clearly states the action (List) and the resource (VibeRooster features the user can pay for) with concrete examples. It also includes the output structure and explicitly ties its usage to the `checkout` sibling, distinguishing it from other tools.

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?

The description provides explicit usage context: 'Call this before `checkout` if you don't already know the grant.' This gives a clear scenario for when to use it. It does not mention exclusions or alternatives, but the condition is specific enough for an agent to decide. Since it lacks explicit when-not-to-use or alternative tool names, it earns a 4 rather than a 5.

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