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

Annotations already flag destructive/openWorld/non-readOnly, and the description adds substantial value beyond them: money is charged to the saved card on raises, batch minimum of 20, the confirm/preview_id handshake, and the 3D Secure/decline path that returns a payment link with nothing added. This is exactly the extra behavioral context the annotations cannot convey.

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 but front-loaded: the core action is stated first, then money implications, then permissions, then the confirmation workflow. Every clause carries distinct, actionable information with no filler.

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?

With no output schema, the description steps in to explain what the quote returns (preview_id and expected_ fields) and what a decline/3DS attempt yields (a payment link, nothing added). For a money-moving mutation tool, everything an agent needs to call it correctly is present.

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 0%, so the description must carry parameter meaning, and it mostly does: action=set, extra_accounts as the desired TOTAL (0 removes all, add 20+ at a time), confirm, preview_id, and the expected_ fields from the quote. workspace_id and expected_interval are not explicitly explained, leaving a small gap.

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?

Names specific verbs (Buy, raise, lower, remove) and the exact resource (Agency extra-account slots), including the action=set semantics. No sibling tool operates on extra-account slots, so the agent can distinguish it immediately.

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 explicit prerequisites (Owner only; billing:write scope) and a full two-step workflow: call without confirm for a quote/preview_id, then call again with confirm=true after user agreement. This is precise when-and-how guidance rather than implied context.

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