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

Annotations already mark readOnlyHint=true and destructiveHint=false, and the description reinforces this with 'without debit' and 'dry-run'. It also adds useful behavioral details about the response, naming cost, balance, and would_succeed.

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?

The description is one dense, well-structured sentence that front-loads the core behavior and includes the endpoint plus response fields. No wasted words.

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 low-complexity tool with one optional parameter and no output schema, the description is complete enough. It explains what the operation does, what it returns, and how it differs from debit operations, while annotations cover safety.

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% and the only parameter, op, is already documented with its default. The description repeats 'op=inbox' but adds no new semantic information about allowed values or behavior beyond the schema.

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 action ('dry-run cost'), the resource ('credit cost'), the endpoint, and the key differentiator ('without debit'). This clearly distinguishes quote_credits from debit-related siblings like checkout_credits and confirm_credits.

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 phrase 'dry-run cost for an op without debit' provides clear context that this is a preview or estimation tool rather than an executing one. It does not name an alternative explicitly, but the no-debit framing makes the appropriate usage evident.

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