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

Annotations already cover the safety profile (readOnly=false, destructive=false, idempotent=false). The description adds genuine behavioral context beyond that: the code is guest-facing at checkout, and it can be attached to a live event or an unclaimed draft via one of two mutually exclusive identifiers. It does not explain duplicate-code handling or permission requirements, so it stops short of a 5.

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?

Three tight sentences with no filler; the purpose and the identifier rule are front-loaded. Slightly terse for the number of parameters it must contextualize, but nothing is wasted.

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 an 11-parameter creation tool with no output schema and no schema descriptions, the definition is thin: it never explains the constraint semantics of max_uses, expiry windows, or applicable_classes, nor what a successful creation returns. The identifier routing and usage trigger are covered, but the parameter surface is largely unaddressed.

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 description coverage is 0% across 11 parameters, so the description must carry the load. It only touches event_id, draft_id, and edit_token (and discount mode implicitly); it says nothing about code, discount_value, enabled, max_uses, starts_at, expires_at, or applicable_classes.

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 ('Create a coupon / discount / promo code'), plus the two discount modes and where the code is redeemed (guest checkout). This cleanly distinguishes it from siblings like bulk_create_promo_codes and create_promo_profile without needing to name them.

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?

Explicit trigger ('Use this when the host asks for a coupon or discount code') and a routing rule for targeting ('Provide either event_id, or draft_id + edit_token'). It does not, however, contrast with bulk_create_promo_codes, which is the obvious sibling an agent might confuse it with.

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