Buy an approved quote (spends money)

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

Annotations cover the safety profile (destructive, non-idempotent, openWorld), yet the description adds substantial context beyond them: charges at most the quoted total, consumes the quote, is irreversible ('cannot be undone from here'), enumerates stop conditions (quote_changed, checkout_mismatch, policy_blocked, low_confidence), and warns that only the 'purchased' outcome means a sale occurred. It also flags result text as untrusted prompt-injection surface.

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?

Dense single paragraph, front-loaded with the action and the spend warning before the caveats. Every sentence carries operational content (preconditions, error codes, irreversibility, untrusted-data warning), though the volume of clauses makes it heavier than an ideal short definition.

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?

There is no output schema, and the description compensates by enumerating the outcome vocabulary, the meaning of 'purchased' versus error outcomes, and the hand-off checkout_url for the shopper. Nothing needed to call this mutation safely and interpret its result is missing.

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% for the single quote_id parameter, so the baseline is 3. The description goes further by establishing provenance ('quote_id from quote_purchase') and reinforcing that the quote must already be approved, which tells the agent where to obtain a valid value rather than just its shape.

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 precise verb+resource ('Buy exactly what an approved quote priced') and immediately distinguishes itself from siblings by declaring it is 'the only tool that can spend money' and by naming quote_purchase, approve_quote and list_orders. An agent can route between buy_quote and approve_quote 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?

Gives an explicit precondition chain ('only after the shopper saw the exact total and said yes and approve_quote recorded it'), names the fallback path when the quote is unapproved ('go back to approve_quote'), and names list_orders as the required check after any error. Both when-to-use and when-not-to-retry are stated.

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