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

The API-parity note ("exactly like POST /v1/coupons/redeem") confirms this is a server-side mutation matching a known endpoint, adding context beyond the readOnly/idempotent hints. However, it says nothing about failure behavior for invalid, expired, or already-redeemed codes, which is the main uncertainty for a non-idempotent redemption.

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?

Three short clauses, front-loaded with the action and scope, then the API-parity and follow-up routing. No padding, though the endpoint reference and the schema's invite-reward example overlap slightly.

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?

An output schema exists, so return values need no explanation, and annotations cover the safety profile. For a single-parameter redemption tool the description is nearly sufficient; the only real gap is error handling for unusable codes.

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 coverage is 100% and there is only one parameter, so the schema already carries the load. The description adds only that codes originate from invite rewards or admin grants, marginal value over the existing "e.g. from an invite reward" schema note.

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 ("Redeem a coupon code... for store credit on this account") and names where codes come from (invite rewards, admin grants), which helps separate it from redeem_gift_code. It does not explicitly name that sibling as the alternative, so the line between the two is implied rather than drawn.

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 downstream context — redeemed credit is spent via buy_pack_with_store_credit or gift_pack — which tells the agent what happens next. It stops short of stating when not to use it (e.g., gift codes belong to redeem_gift_code) or any preconditions on the code.

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