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

Annotations declare a non-read-only, non-destructive write with idempotentHint=false; the description usefully adds the required 'billing:authorize' scope and the crucial 'charges nothing' clarification so an agent does not mistake this for a real purchase. It does not say what record is created or returned, but the safety/mutation profile is well covered.

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 tight sentences plus a scope fragment; the core action is front-loaded and every clause (budget, cap, expiry, no charge, required scope) carries distinct information. No filler or repetition of the tool title.

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?

Covers the essential authorization semantics for a 7-parameter mutation, and with no output schema the description arguably should hint at what is returned (authorization id, remaining budget). The bigger gap is that this crowded sibling set includes 'create_spending_authorization', which the description never contrasts.

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 57%, so the description must carry some of the load. It maps well to budget_cents, max_order_cents and expires_in_days and characterizes the offers enum as plan periods/passes/listing time. It says nothing about accept_terms (including agent_authorization) or idempotency_key, leaving the two least self-explanatory parameters unaddressed.

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 (delegate/authorize prepaid credit) and enumerates the resources it covers: plan periods, posting passes, listing time. That is far more than a restatement of the name. It does not, however, distinguish itself from the near-identical sibling 'create_spending_authorization' or from 'authorize_board_purchases', so an agent cannot tell them apart without opening both 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?

'Charges nothing' implicitly signals this is a budget/permission grant rather than an actual purchase, which is genuinely useful routing information. But it never states when to prefer this over create_spending_authorization, authorize_board_purchases, or authorize_board_post_time, and gives no preconditions beyond the required scope.

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