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

With no annotations, the description carries the behavioral burden. It discloses that the action is staged, requires authentication, returns an actionId, and must be followed by executeConfirmedAction if the user approves. This is the key safety-relevant behavior. It could add what 'stage' implies about balance holds or expiry, but the critical two-phase behavior is clearly stated.

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?

Three short sentences front-load the core action, then provide authentication, required parameter, and the return/confirmation flow. No fluff or repetition of schema details beyond the essential required-parameter note.

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 no-output-schema action tool, the description explains the return value (actionId), the prerequisite (authentication), and the mandatory follow-up (executeConfirmedAction). It is complete enough for an agent to handle the normal flow safely. Minor gaps like expiration of the actionId or behavior on insufficient balance are not covered.

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 covers 50% of parameters: sessionKey has a full description, but invoiceId does not. The description adds that invoiceId must refer to an outstanding invoice, which is meaningful, but it largely repeats the required/string information already in the schema. It does not fully compensate for the missing schema documentation of invoiceId semantics or mention where to obtain it.

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 states a specific verb and resource: 'Stage payment of an outstanding invoice from account balance.' It clearly communicates that this tool only stages the payment, not finalizes it, and the follow-up to executeConfirmedAction is named. This differentiates it from sibling payment-related tools.

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?

It gives clear context for when to use the tool: for outstanding invoices paid from the account balance, and it specifies the required next step (call executeConfirmedAction after user approval). It does not explicitly enumerate alternatives or state when not to use it, so it stops short of a 5.

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