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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=true, so the safety profile is covered. The description's one addition beyond structured data is the required write scope, which is genuinely useful, but it doesn't explain what the destructive flag means here (e.g., whether setting quantity to 0 or omitting it drops the association).

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?

Two short sentences with zero padding. The core action is front-loaded and the auth requirement follows immediately; every clause 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?

For a simple two-parameter field update with rich annotations and no output schema, the description covers purpose, key, and auth adequately. It stops short of noting idempotency implications or what happens on an unknown/invalid association ID, but nothing essential for invoking 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 description coverage is 100% and both parameters (id, quantity) are documented in the schema with format and minimum constraints. The description restates 'quantity' and 'by ID' without adding syntax, defaults, or edge-case meaning beyond the schema, so baseline 3 applies.

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 (Update), resource (asset-part association), the exact field it mutates (quantity), and the key (by ID). This clearly separates it from create_asset_part and delete_asset_part, though it does not explicitly name a sibling to route around.

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?

Provides a real prerequisite in 'Requires asset_parts:write scope', which tells the agent what auth is needed before calling. However, there is no explicit when-to-use vs when-not guidance (e.g., use create_asset_part to establish an association, this only for changing quantity), so usage is only implied.

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