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

Annotations only supply destructiveHint=true, but the description adds rich behavioral context: auth required, ZIP must match the quote, packages are not resent, and detailed billing semantics (terms accounts billed on terms, others drawn from Warp balance with card covering shortfall). This is exactly the value-add beyond structured fields that a booking mutation needs.

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?

Purpose is front-loaded in the first sentence, and every following sentence carries real constraints (prerequisites, ZIP matching, billing, confirmation). It is dense and parenthetical in places, but there is little waste.

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, auth-gated, billing mutation with no output schema, the description covers prerequisites, confirmation, and charge behavior thoroughly. It stops short of describing the return value (e.g., a booking id), which is the only notable gap given no output schema exists.

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 100%, so baseline is 3, but the description adds meaning: quote_id must come from the user's chosen option, pickup can be omitted only when a default shipper is saved, and ZIPs must match the quote. These behavioral constraints on parameters go beyond the schema text.

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+resource ('Book a FedEx parcel option') and ties it to its upstream source (parcel_quote). This clearly distinguishes it from generic siblings like book, batch_book, and multistop_book, which an agent can rule out without opening schemas.

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?

Gives a clear precondition chain: derive the option from parcel_quote, then 'Only call after the user explicitly confirms this option and price.' It implies-when without exhaustively naming alternatives, but the confirmation gate and quote dependency are explicit.

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