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

With only readOnlyHint=false and idempotentHint=false, the description carries the burden of disclosure. It explains that the tool returns a payment URL, credits land automatically after payment, and mentions the output per method. It does not mention potential side effects like link expiration or rate limits, but it does not contradict annotations and provides sufficient transparency for safe invocation.

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 two sentences, front-loading the core purpose, then detailing the two methods and follow-up. Every sentence is informative and non-redundant. Perfectly concise for the complexity.

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?

Given that output schema exists, the description need not detail return values, yet it briefly does. It covers parameter explanation, behavioral steps (get link, pay, credits land), and a confirm step. It also mentions authentication. For a tool with 2 parameters, this is highly complete.

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% (baseline 3). The description adds value by explaining how the 'method' parameter affects the output (stripe returns checkout_url, crypto returns invoice_url + txn_id) and implies the range for amount_usd. This enriches the parameter meaning beyond the schema alone.

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?

Description clearly states the tool's purpose: 'Get a machine-usable payment link to top up credits.' It specifies the verb 'Get' and the resource 'payment link', and distinguishes between two payment methods. It also mentions the requirement for a Bearer API key, leaving no ambiguity about what the tool does relative to siblings like get_account.

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 provides clear context for when to use the tool (to top up credits) and includes post-usage guidance to 'confirm with get_account.' It does not explicitly state when not to use it or list alternatives, but the purpose is distinct enough among siblings. The guidance is adequate though not exhaustive.

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