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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: it's a dry-run that does not debit, and it returns would_succeed, which implies the tool can predict success without executing. This goes beyond the annotations by explaining the non-mutating quote behavior.

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 sentences with no waste. The first sentence states the core purpose and endpoint, the second lists the return values. All information is front-loaded and relevant.

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 simple read-only quote tool with one optional parameter and no output schema, the description is nearly complete. It covers the operation, the non-debit behavior, and the key return fields. It could mention that 'op' accepts other values beyond ocr, but the schema already documents that. The absence of an output schema is compensated by listing the return fields in the description.

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%, so the single parameter 'op' is already documented in the schema. The description adds the default value ('Defaults to ocr') and shows an example value in the endpoint path, which is helpful but not extensive. Baseline 3 is appropriate since the schema does the heavy lifting.

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 clearly states the tool's purpose: a dry-run cost quote for an operation without debiting credits. It names the specific endpoint (GET /credits/quote?op=ocr) and the key outputs (cost, balance, would_succeed), distinguishing it from actual debit operations like checkout_credits or 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 description implies when to use it: when you need to check cost before performing an operation, without debiting. It doesn't explicitly name alternatives or exclusions, but the 'dry-run' and 'without debit' phrasing clearly separates it from sibling tools that perform actual credit transactions. The sibling context (checkout_credits, confirm_credits) reinforces this distinction.

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