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

Annotations already declare readOnlyHint=true and destructiveHint=false, and the description reinforces this with 'without debit.' It also adds useful behavioral detail beyond annotations: the endpoint shape and the fact that it returns 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 extremely concise: one sentence conveys purpose, endpoint, debit behavior, and return fields. Every phrase earns its place and the most important constraints are front-loaded.

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, mentioning the return fields is valuable and mostly sufficient. It is slightly incomplete because possible op values beyond 'digest' are not enumerated, even though the title hints at rss digest, atom feed, and feed items.

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 for the single parameter is 100%: 'op' is already described as the operation to quote with a default of digest. The description adds only an example URL and does not significantly expand parameter meaning 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 for an operation without debiting. It names the resource/endpoint and the return fields, and the 'without debit' framing clearly distinguishes it 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?

It is clear you use this tool when you want a no-debit cost estimate before performing an operation. However, it does not explicitly name the alternative tools that would actually perform the debit, so it stops short of explicit when-not-to-use guidance.

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