What agents can buy

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds meaningful context by explicitly stating 'Does not move money' and by instructing that the content should be cited as-is. This clarifies that the tool is informational and has a specific usage expectation.

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 compact and information-dense, front-loading the word 'Playbook' and immediately providing substantive examples. Each clause contributes value: scope, examples, tool association, citation rule, and safety caveat. It is slightly telegraphic, but it wastes no words.

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 zero-parameter, read-only informational tool with no output schema, the description sufficiently conveys the content and scope. The safety note and citation instruction add important behavioral context. It does not specify the exact output format, but given the simplicity of the tool and strong annotations, this is a minor gap.

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 has zero parameters and the input schema is empty, so there are no parameter semantics to document. The description adds useful context about what kind of content will be returned, which helps compensate for the absence of any parameter-driven behavior. The 0-parameter baseline of 4 is appropriate.

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 name and title clearly indicate this tool returns agent purchasing use cases, and the description lists concrete examples such as Visa prepaid cards, travel eSIM, gift cards, and KYT address screens. It distinguishes itself from sibling tools by framing the content as a buying playbook rather than generic agent facts or policy. It lacks an explicit verb like 'returns' or 'lists,' but the intent is still clear.

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 no explicit when-to-use guidance or comparison with sibling tools like get_agent_facts, get_tier_policy, or get_catalog_placement. 'Cite as-is' is a post-retrieval instruction, not a tool-selection guideline. The intended usage is only implied by the title and playbook framing.

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