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

Annotations indicate it's a non-read, non-destructive, non-idempotent operation, so the bar for extra disclosure is lower. The description adds valuable behavioral details: codes are uppercased server-side and the value is a string interpreted differently for percentage vs fixed_amount. These are non-obvious, useful behaviors beyond what annotations provide.

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 two sentences: the first states the purpose, the second provides key parameter and server-side behavior. Every word earns its place, and the most important information is front-loaded. It is appropriately sized for a tool with rich schema coverage.

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?

With 17 parameters and an output schema, the description doesn't need to enumerate every field. It covers the critical cross-parameter semantics (type/value) and server-side uppercase behavior, which are not apparent from the schema or annotations. Optional fields like posEnabled are already self-descriptive in the schema, making the description sufficiently complete for 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?

Input schema already covers all 17 parameters with descriptions (100% coverage), so the baseline is 3. The description adds semantic meaning for type and value, clarifying the relationship between them and explaining the string-based value format ('10' = 10% or 10 currency units). This reduces ambiguity that the schema alone leaves unresolved.

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 'Create a promotion / discount code,' which uses a specific verb and resource. It clearly distinguishes from related tools like update_promotion, list_promotions, and delete_promotion by focusing on creation. The purpose is unambiguous and actionable.

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 clear context: this tool is for creating promotions and discount codes. It doesn't explicitly mention when not to use it or point to alternatives, but the context is sufficiently clear for an agent to infer when to invoke it. No exclusions are given, which aligns with a score of 4.

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