apply_coupon

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

With no annotations provided, the description carries full burden but only states the action without behavioral details. It doesn't disclose if this requires authentication, has side effects (e.g., modifies order state), rate limits, or error conditions (e.g., invalid codes). For a mutation tool, this is a significant gap in transparency.

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 a single, efficient sentence that directly states the tool's function without redundancy. It's front-loaded with the core action and purpose, making it easy to parse quickly.

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 this is a mutation tool with no annotations and no output schema, the description is incomplete. It lacks crucial context like success/failure behavior, return values, or interaction with other tools (e.g., order state changes). For a tool that modifies data, more detail is needed to guide the agent effectively.

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 has 100% description coverage, with the 'code' parameter well-documented in the schema itself. The description adds no additional parameter meaning beyond implying it's for discounts, which is already clear from the tool name and context. Baseline 3 is appropriate as the schema does the heavy lifting.

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 clearly states the action ('apply') and target ('coupon or promo code to the current order for a discount'), making the purpose understandable. However, it doesn't explicitly differentiate from siblings like 'get_rewards' or 'checkout', which might also involve discounts or order modifications, so it misses full sibling distinction.

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 provides minimal guidance by implying usage on 'the current order', but offers no explicit when-to-use rules, prerequisites (e.g., order must exist), or alternatives (e.g., vs. 'checkout' or 'get_rewards'). This leaves the agent with little context for tool selection.

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