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

Annotations already establish that this is a non-read-only, idempotent, non-destructive operation. The description adds important behavioral context by explaining that invalid, expired, or already-used codes return 'redeemed: false' as an ordinary result rather than an error, which helps the agent interpret responses correctly.

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 short, front-loaded with the core action, and every sentence adds useful information. The note about invalid codes being an ordinary answer prevents a common misinterpretation, and the final note about sending letters clarifies scope.

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?

Given the simple one-parameter schema, rich annotations, and existing output schema, the description is nearly complete. It covers the main action, expected failure semantics, and the important follow-up that letters must still be sent, though it could say more about whether codes can be redeemed across accounts or reused after success.

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 schema only declares a string parameter named 'code' with no description, so the description must supply meaning. It does so by clarifying that the code is a promo code or a gift code from a printed letter, though it does not specify formatting details such as case sensitivity or whitespace handling.

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 description uses a specific verb, 'Redeem,' and precisely identifies the resource as a promo or gift code from a printed letter. It also states the effect, adding letters to the account, so the agent can distinguish this from sibling tools without opening the schema.

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 makes the use case clear: redeem codes from printed letters to add letters to the account. It does not name explicit alternatives, but no sibling tool appears to overlap with this function, and it adds a useful postcondition that letters must still be sent afterward.

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