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

Annotations already declare idempotency and open-world behavior, and the description adds genuinely new context: it spends prepaid credit, needs a specific scope, and uses a durable purchase key to prevent duplicate debits. It does not explain what happens on insufficient credit or rejected max price, but the core risk profile is disclosed.

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 compact clauses, with the action and the anti-duplicate guarantee front-loaded. No wasted text, though it could have folded in the quote prerequisite in the same space.

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 money-moving mutation with six required parameters and no output schema, the description covers the scope and payment mechanism but omits the prerequisite quoting step and any description of the success result (e.g., the new expiry). Annotations carry the safety profile, so the remaining gap is moderate rather than severe.

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 only 43%, and the description names no parameters at all. Critical inputs such as expected_expires_at (must match the quote's current expiry) and max_price_cents (a refuse-above ceiling) are only partly documented in the schema, and the narrative does not compensate.

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 and resource ('Buy additional post time') plus the payment source ('prepaid credit'), so an agent can distinguish it from quote_board_post_time and authorize_board_post_time. It stops short of naming those siblings or the fact that this is the terminal step of a quote→authorize→buy flow.

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 purchase intent and the required 'boards:extend' scope imply when to call it, but nothing states that a quote must be obtained first, nor how it differs from the sibling authorize/buy_board_pass tools. Usage is inferred rather than directed.

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