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

Annotations already declare destructiveHint=true and idempotentHint=false, so the description should clarify what that means here — e.g. that repeated calls append duplicates rather than replacing items, and whether estimate totals are recalculated. It says none of this; 'Adds' is the only hint at append semantics.

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 zero filler, so nothing is wasted — but the brevity comes at the cost of substance for a nested, up-to-100-item mutation. Efficient, not adequate.

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 single-purpose append tool with no output schema, one sentence stating the verb and target is genuinely enough; the description needn't explain return values or list every field. The main omission is that it doesn't distinguish this from its near-identical siblings.

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?

With 67% schema coverage and no parameter discussion in the description, nothing is added beyond the schema. The description doesn't explain the section_id default ('first section'), the 100-item cap, or how quantity/unit_cost/markup_percent combine into the priced line — all behaviors the schema alone leaves implicit.

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: 'Adds priced line items to an existing estimate.' The word 'existing' implicitly separates it from create_estimate, but it never names add_change_order_items or add_invoice_items, which are near-identical siblings an agent could easily confuse it with.

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 guidance on when to use this versus add_change_order_items or add_invoice_items, no prerequisite checks (does the estimate need to be in draft?), and no mention of what happens on repeated calls despite idempotentHint=false. The agent must infer everything from the name.

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