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

Annotations carry no read-only or idempotency reassurance, so the description must carry the behavioral burden. It does so by disclosing that this is a mutating, immediately-charging operation with a deterministic price and no seller round-trip. It also notes shared delegation/envelope enforcement with services_accept_quote. This is substantive behavior disclosure beyond the annotation fields.

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 sentences, no filler, and the most decision-relevant facts are front-loaded: fixed-price purchase, one-call, no seller round-trip, immediate charge, and the enforcement parallel. Every clause adds information needed for selection or invocation.

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 seven-parameter, no-output-dchema tool with nested objects and a real charge side effect, the description gives a strong high-level flow. The schema documents the parameters, including the confirmation_token kickback and payment-method fallback behavior. It lacks an explicit statement of return/error behavior and the full required-action/declined paths, but the combination of description plus rich schema is close to sufficient.

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%, so the input schema already documents all seven parameters in detail. The description adds no new parameter-level meaning beyond framing the overall flow (scope validation, immediate charge). Baseline 3 is appropriate because the schema does the heavy lifting.

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?

The description opens with a specific verb and resource: 'Buy a fixed-price service in one call.' It then enumerates the exact behaviors (validates scope, computes deterministic price, creates quote thread in accepted, charges immediately) and distinguishes itself from the quote round-trip flow. An agent can clearly tell this from services_accept_quote and other services_* siblings.

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?

The description provides clear context for when to use the tool: for a fixed-price service purchase in a single call with no human seller round-trip. It references the analogous services_accept_quote enforcement but does not explicitly state when not to use it or name alternatives beyond that single reference.

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