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

Annotations already flag it as a non-read-only, non-idempotent write, but the description adds the crucial nuance that the call itself mutates nothing, returns a preview plus a confirmation link, and requires merchant action to take effect. It also documents the money unit convention. This is exactly the kind of behavior an agent cannot infer from 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?

Four short, front-loaded sentences with essentially no waste. The money-unit sentence is slightly misplaced between the purpose and the workflow explanation, but every sentence earns its place.

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?

No output schema exists, yet the description covers what the call returns (a preview of changes and a confirmation link) and who can execute it. For a 3-parameter write tool with a nested object, nothing an agent needs in order to call it correctly is missing.

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 coverage is 100%, so the baseline is 3, but the description adds a unit convention (money in integer minor units/cents) that the schema does not state. The nested `values` object detail is otherwise left to the schema, so it does not fully reach a 5.

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?

"Make or change a popup" states a specific verb and resource, and the upsert nature (create when no id, edit when id given) is unambiguous against siblings like popups_list and popups_remove. An agent can select this tool without opening the schema.

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 explains the full workflow context: calling it produces a preview and confirmation link rather than an immediate change, and only the merchant can finalize. That is strong usage context, though it never states when to prefer this over popups_remove or popups_list or any exclusions.

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