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

Annotations already declare idempotentHint=true and destructiveHint=false, but the description adds real operational context: the exact weekly reset boundary, the credit yield (~1 house-bot hour), and the registered-key auth requirement. 'Safe to retry' reinforces idempotency with an explicit retry posture rather than leaving it implicit.

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?

Front-loaded with the summary and telegraphic WHEN semantics; every clause carries information (quantity, cadence, reset time, retry safety, auth, example). The staccato labels are efficient though slightly terse for prose clarity.

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 zero-required-param claim tool with no output schema, the description covers yield, frequency, reset boundary, retry safety, and auth, which is enough to invoke it correctly. Only a note on the already-claimed response is missing.

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 single key parameter is already documented as 'Registered keys only.' The description's 'Registered key required' and the '{}' example reinforce the optional/omittable nature of the param but add little beyond the schema, so the baseline 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 and resource ('claim the free weekly drop of 10 Arena credits') with a concrete quantity and cadence, so an agent can distinguish it from daily claims. It stops short of naming a sibling alternative, but the weekly/10-credit scope is unambiguous.

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 'WHEN:' framing gives explicit usage context, and 'Once per week (weeks start Monday 00:00 UTC)' effectively states the condition under which the tool should not be called again. No sibling alternatives are named, but the eligibility window is fully specified.

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