Services purchase

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

The description fully discloses the tool's side effects: it 'validates the scope, computes the deterministic price, creates the quote thread directly in accepted, and charges immediately.' It also notes that it operates without human seller interaction. This goes beyond the annotations (which only indicate false readOnly and idempotent) by specifying the actual state-changing operations performed.

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?

The description is two sentences: the first clearly states the main action and internal behavior, and the second provides a useful cross-reference to a sibling tool. It is concise, front-loaded, and free of fluff or 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 the tool's moderate complexity (multiple parameters, confirmation flow hinted in the schema), the description covers the primary purpose and high-level behavior well. It does not explicitly mention the confirmation_required kickback flow or that a retry may be needed, but these details are present in the schema and annotations, so the description is reasonably 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?

The schema itself has 100% parameter description coverage, so the tool description does not need to repeat parameter details. However, the tool description adds no parameter-level meaning beyond what is already in the schema. Since coverage is high, the baseline is 3, and there is no additional parameter insight to warrant a higher score.

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 clearly states the tool's purpose: 'Buy a fixed-price service in one call.' It specifies the resource (fixed-price service) and the action (buy), and distinguishes it from quote-based flows by noting 'no human seller round-trip' and 'creates the quote thread directly in accepted.' This makes it immediately obvious when to use this tool versus quote-based alternatives.

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 gives clear context for when to use the tool: for fixed-price services with immediate purchase and no negotiation. It also references 'Same delegation/envelope enforcement as services_accept_quote' for payment handling. However, it does not explicitly state when not to use it (e.g., when a listing requires manual quote approval), so it lacks an explicit exclusion clause.

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