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

Adds substantial context beyond annotations: 'Nothing is charged and you never pay,' the two-phase async flow, the returned verify_url and user_code handed to the account holder, and the required human confirmation before payment. This tells the agent this is not idempotent in practice and must be followed up, which the hints alone do not convey.

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?

Two sentences, zero filler. The most important fact (no charge, agent never pays) is front-loaded, followed by the return values and the required follow-up call.

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?

No output schema exists, yet the description explains what is returned (verify_url, user_code) and the lifecycle continuation (poll get_purchase_request), plus the human-in-the-loop requirement. Nothing an agent needs to invoke and correctly handle this tool 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 id, tenant and version are fully documented in the schema (including provenance from search_sessions and the default for version). The description adds no parameter-level detail, so baseline 3 applies.

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+resource ('Start buying a paid marketplace listing') and immediately scopes it: it is a request step, not an actual purchase. This is clearly distinguishable from search_sessions (find listings) and get_purchase_request (poll status), which it names.

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 context for use ('for the account holder to confirm') and an explicit next step: 'Then poll get_purchase_request.' It does not state a when-not condition, but no sibling overlaps this write-style action, so the routing is unambiguous.

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