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

No annotations are provided, so the description carries the full burden. It usefully discloses the once-only extension rule and the TTL-based mechanism, which is real behavioral value. It does not disclose permissions, whether an expired offer can be extended, or what happens on refusal beyond the bare statement.

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 tight sentences with the core action first and the key limitation second. Every word earns its place; nothing is padded or repeated from the name.

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 single-parameter, no-output-schema mutation, the description covers what it does and its main constraint. It is only slightly thin on preconditions and the outcome of a refused extension, which an agent might want to know 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?

With a single parameter at 100% schema description coverage, the schema already defines offerId as the offer to extend. The description adds no format, source, or lookup detail beyond that, so the baseline of 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 (extend) and resource (an offer's validity) with the mechanism (its TTL), so the action is unambiguous. It does not explicitly differentiate from siblings like get_offer or cancel_checkout_session, but they are unrelated operations, so confusion risk is low.

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 implies the usage context (extending an offer's validity) and reveals a hard constraint that affects when it can be called (only once). However, it never names alternatives or states the precondition under which extension applies, e.g. whether the offer must still be active.

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