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

Beyond the readOnly/openWorld annotations, it discloses the non-obvious response contract: a 200 can contain per-carrier errors with success false, and a quote of 0 means the carrier cannot take the parcel. It also states the side-effect profile (no booking, no charge) and a hard input limitation (dangerous goods), which is exactly the context annotations cannot carry given there is no output schema.

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?

Five short sentences, front-loaded with what the tool does and does not do, then the toggle, then the response caveats. Every sentence carries information an agent would otherwise have to infer.

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?

Strong for a 13-parameter, no-output-schema tool: it covers the mutation-free nature and the error/zero-quote return semantics. It leaves the conditional parameter requirements (priority/on-demand/international) to the schema, so an agent must still read the schema to know which optional fields become mandatory.

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 77%, so the schema already documents most parameters. The description's only parameter-level contribution — return_all_quotes defaulting to cheapest or fastest — largely restates the schema's own description, and it adds no guidance on service_levels, features, or the conditional requirements (order_date for priority, dropoff_address for on-demand, dutiable_amount for international).

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 ('ask the carriers for a price and delivery estimate') plus the resource and scope ('for given parcels', 'to a destination'). Clearly separable from siblings like shippit_book_orders and shippit_create_order, which perform the mutation this tool deliberately does not.

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?

Explicitly frames the tool as a pre-booking enquiry ('Nothing is booked and nothing is charged'), which tells an agent when to reach for it versus the booking siblings, and gives a toggle ('Set return_all_quotes to see every carrier'). It adds one real exclusion ('Dangerous goods cannot be quoted') but never names a sibling as an alternative, so it stops short of full when/when-not routing.

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