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

Annotations declare readOnlyHint=false and destructiveHint=false, so the safety profile is partly given. The description adds the critical behavioral fact that no charge or label purchase occurs here, which an agent cannot infer from annotations alone. It stops short of discussing auth or idempotency, so not a 5.

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?

Front-loads the create-and-rate action, then the key negative constraint, then the API endpoint. Every clause earns its place with no redundancy.

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?

Given nested objects, no output schema, and 5 params, the description covers inputs, behavior, the non-charge guarantee, a return hint (available rates), and the API route. It could say more about the optional carrier_accounts filter for rating scope, but it is largely complete.

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% with detailed nested field docs (weight in OUNCES, ISO country codes, etc.), so the schema carries the parameter burden. The description only restates the three required inputs and adds no format or syntax detail 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 (Create a shipment) and resource, names the exact required inputs (to_address, from_address, parcel), and clarifies scope: it returns rates rather than buying labels. This distinguishes it from easypost_buy_shipment without opening either 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?

Explicitly states when to use it (to get rates) and when not to (it does NOT purchase a label or charge the account), and names the alternative easypost_buy_shipment for buying. Nothing is left to inference.

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