Redeem a fmrl.site key code

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

The annotations already declare destructiveHint=true and idempotentHint=false, and the description adds substantial context beyond them: the code works once, for 10 minutes, a spent or expired code fails with the current key kept, the replaced key's ring stays in the file, and FMRL_API_KEY short-circuits redemption. These are real failure-mode and side-effect disclosures. It could say more about what a rotation does to in-flight sessions, but the coverage is well above the bar the annotations set.

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?

Purpose is front-loaded in the first clause, followed by format, usage constraint, alternative, and failure behavior in a tight sequence with no filler. The single semicolon-linked paragraph is dense, and splitting the failure-mode sentence out would improve scanability.

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 one-parameter mutation whose return value is covered by an output schema, nothing an agent needs is missing: prerequisites, alternative tool, side effects, failure behavior, and the environment-variable override are all present.

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 the schema already says dashes, spaces and case do not matter. The description still adds meaning by describing the code's shape: 26 letters and digits in groups of four, such as K7QX-M2PA-…, so an agent can recognise a valid code before calling. That goes slightly beyond 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?

The description states a specific verb and resource: trade a key code for the fmrl key it carries, then install it as this machine's key in its credentials file. It also explicitly names fmrl_rotate as the sibling it is not, so an agent can distinguish the two tools without comparing schemas.

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 an explicit when: the person hands over a code, with the literal phrasing 'Redeem my fmrl key code …'. It gives an explicit when-not: to replace this machine's own secret, use fmrl_rotate. The condition that selects the alternative is named, not inferred.

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