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

Annotations already declare readOnlyHint=false, destructiveHint=false, openWorldHint=true, so the safety profile is covered. The description adds useful audience/rail context but discloses nothing about what the call produces, auth needs, or lifecycle beyond the annotations. With annotations carrying the burden, a 3 is appropriate.

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 tight sentences, front-loaded with the core purpose and followed by the routing exclusions. No filler, every clause earns its place.

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?

An output schema exists so return values needn't be described, and annotations cover safety. However, for a four-parameter payment-creation tool with zero schema coverage, the absence of any parameter guidance leaves an agent unable to invoke it correctly without external lookup.

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 description coverage is 0% and the description never mentions any of the four parameters (packageId, platform, cancelUrl, returnUrl) or their meaning. It fails to compensate for the coverage gap; packageId being required and where to obtain it is left entirely unexplained.

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?

States a specific verb (Creates) and resource (crypto/NOWPayments invoice) with a scoped audience (human web/Telegram top-ups). It explicitly separates itself from sibling paths (Stripe checkout, x402 USDC) so an agent can route without opening a schema.

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?

Gives explicit when-to-use (human web/Telegram top-ups), when-not-to-use (ChatGPT humans should use the web URL), and names the correct alternative for bots (USDC on Base via x402). This is textbook routing guidance.

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