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

Adds substantial behavior beyond the annotations: it operates only on saved checks, performs no fetch/scan/login, is advisory and never proceeds past payment, explains grade expiry at 30 days and that an ungraded store is not penalized, and specifies the error envelope {code, message, next_step}. It also clarifies that a false or unknown reaches_checkout is not a definitive no, which an agent would otherwise misread.

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?

Front-loads the trigger before the return-field inventory, which is the right order. The long enumeration of return fields is dense but justified because there is no output schema; a slightly tighter list would improve scanability without losing information.

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 no output schema, the description carries the full burden of explaining returns, and it does so field by field, including conditional fields like alternatives_hint and grade_note. Error shape, non-goals, and the advisory stopping point are all covered, leaving nothing an agent needs missing before calling.

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?

Only one parameter with 100% schema coverage, so the schema already defines url as a store or product URL. The description reinforces this with a concrete example call and the alternate form, adding modest but real value over the 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 specific verb and resource: verifies whether an agent can reach checkout at a given store, using saved checks. The phrasing 'can my agent check out at <store>?' plus the example call makes the intent unmistakable and distinguishes it from siblings like can_agent_checkout or precheck.

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 a clear trigger: call right before the agent attempts checkout, or when a user asks whether checkout is possible at a store. 'Saved checks only: no store fetch, no scan, no login' sets the boundary for when this tool is insufficient, though it does not explicitly name the sibling (e.g. precheck) to use for a live scan.

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