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

Beyond annotations (readOnlyHint=false, idempotentHint=true), the description discloses critical behaviors: credit lands within 1-2 minutes, some codes are gated on KYC approval, the claim locks instantly, and list_codes is a gated tool accessible by name. This adds significant context not present in structured fields.

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 front-loaded with the core purpose and uses three sentences, each earning its place. The second sentence explains timing and KYC exceptions, the third offers a useful pointer to list_codes. No wasted words.

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?

The description fully covers what an agent needs to know: purpose, idempotency, delay, KYC dependencies, and a hidden tool reference. An output schema exists to explain return values, so no additional return-format information is required.

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 covers the only parameter (code) with a clear description that case and dashes are forgiven. The tool description adds no additional parameter syntax, but it does provide behavioral context such as idempotency and KYC gating. This meets the baseline for high schema coverage.

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 opens with a specific verb and resource: 'Redeem a promo code that adds money to the user's cash balance.' This clearly states what the tool does and distinguishes it from similar siblings like redeem_rewards or add_funds by focusing on promo codes and cash balance.

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 implies when to use (when a user provides a promo code) and adds contextual guidance (each code works once per user, delay, KYC conditions). It also mentions list_codes as an alternative for viewing history, but does not explicitly exclude other tools or name alternatives for redeeming.

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