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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the safety profile is covered structurally. The description adds nothing behavioral: it never mentions the two-phase preview/confirm flow implied by the confirm_id parameter, nor that the write overwrites existing MFN quantity, which is exactly the context an agent needs before a destructive call.

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?

A single front-loaded sentence with no wasted words, but its brevity reflects under-specification rather than disciplined conciseness, so not a 5.

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 a destructive mutation with a two-step confirmation protocol, no output schema, and half the parameters undocumented, a one-line description is materially incomplete. The agent lacks the confirm_id workflow, the account_id scoping rationale, and any effect/reversibility information.

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 only 50%: sku and quantity carry no schema descriptions, and the description never clarifies their format or semantics. The one genuinely non-obvious behavior in the schema, the confirm_id preview-then-execute token, is left unexplained in the description, so it fails to compensate for the coverage gap.

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 gives a specific verb and resource ('Update MFN inventory quantity') scoped per SKU, which is clear enough for an agent to know what it mutates. It does not differentiate itself from siblings such as bulk_update_inventory or ads_stockout_check, 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 use this single-SKU update versus bulk_update_inventory, nor any prerequisite conditions. The agent must infer the selection context entirely from the name.

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