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

With no annotations, the description must carry behavioral weight, and it does add genuine traits beyond the schema: binding is owned by the coupon and survives re-pricing, and an unbound coupon discounts nothing. It still omits permission/authority requirements, what a duplicate name does, and the role of dpop_token on a mutation call, so the disclosure is partial.

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 action is front-loaded in the first sentence, and the binding explanation follows with no filler. The second paragraph is longer than strictly required but each clause carries distinct information about coupon semantics.

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 output schema means return values need not be described, and 7 of 8 parameters are self-documented. However, for an unannotated mutation that requires operator authority and takes a dpop_token, the definition never states the authorization or error context an agent would need before calling it.

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 88%, so the schema already explains name, tool_ids, discount_percent, and the validity window. The description reinforces tool_ids semantics and adds the empty-binding consequence, but says nothing about the undocumented dpop_token, leaving the baseline 3 appropriate.

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 opening sentence gives a specific verb and resource: 'Create a new operator-owned discount coupon.' Combined with the name and the sibling set (update_coupon, delete_coupon, list_coupons, redeem_coupon), an agent can identify this as the creation endpoint. It does not, however, name or contrast any sibling explicitly, so it stops short of a 5.

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?

There is no statement of when to choose this tool over brain_update_coupon, brain_list_coupons, or brain_redeem_coupon, and no prerequisites (e.g. operator authority) are given. The only contextual clue is that 'patrons redeem it' while the operator mints it, which is suggestive but not usable guidance.

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