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

Goes well beyond the annotations: it discloses that the ledger records tip_received with an amount band and never who, that the link is one-time, and that the operation buys/changes/mints nothing. It also states the floor price and payment methods.

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?

Three sentences totaling roughly 45 words, with the primary output front-loaded. Every sentence earns its place: output, side-effect negation, and usage instruction.

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 single-parameter tool with annotations and no output schema, this is complete: it covers return type, payment methods, ledger behavior, privacy, floor, and the next step for the caller.

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%: amount_cents has a description ('Default 500'), minimum, and maximum in the schema itself. The description adds the 'Floor $3' context but does not significantly extend the meaning already provided by 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?

States a specific verb and resource: 'Returns a Stripe Checkout link (card or USDC) for a one-time coin.' It also differentiates from siblings by explicitly negating other effects ('buys nothing, changes nothing, mints nothing') and naming the ledger record type.

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 gives useful context ('keeps the lights on', 'one-time coin') and an instruction ('Give the link to whoever holds the wallet'), implying when to use the tool. However, it does not explicitly name alternative tools or state when not to use it.

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