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

Annotations already mark this as a non-read, non-idempotent mutation. The description adds valuable behavioral detail: the returned api_key is shown once, the token has lifecycle errors like letter_claimed and letter_expired, and passing public_key carries identity. This substantially explains the one-shot nature of the operation.

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 compact and front-loaded: the core redemption action and return behavior come first, followed by the optional identity parameter and a concise error list. Every sentence adds value without repetition.

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 there is no output schema, the description adequately covers the return value (api_key shown once) and the relevant error cases. It could slightly expand on what happens if public_key is omitted, but the current phrasing is sufficient for correct invocation.

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%, so both parameters are already documented with types and descriptions. The main description adds the practical hint that public_key is optional and carries identity, but it does not need to compensate for missing schema information.

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 states a specific verb ('Redeem') and resource ('a Letter token') and clarifies the result: a Tourist month in exchange for the token, returning an api_key shown once. This clearly distinguishes it from sibling issue_letter and other continental tools.

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 gives clear context on how to use the tool: redeem a token, optionally pass a public_key to carry identity over, and expect specific errors. It does not explicitly name alternatives or exclusion conditions, but the redemption scenario is clear enough to route an agent correctly.

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