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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds substantial context beyond them: 422s are not charged, typical 1-3 s latency, USD 0.002 price, a 10-reads-per-IP-per-UTC-day free tier, and a prompt-injection warning to treat returned page text and on-chain strings as untrusted data.

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?

Dense and front-loaded: the core question comes first, then scope, error behavior, cost and a security note. Each clause earns its place, though the run-on punctuation makes it slightly harder to scan than a sentence-per-topic layout would.

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 need not be spelled out, yet the description still sketches the payload and verdict shape. Combined with coverage of errors, pricing, rate limits, chain support and untrusted-data handling, an agent has everything needed to invoke it correctly.

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 100%, so the baseline is 3; the description still adds semantics by explaining that the `verdict` is computed against `expect_pay_to`, `expect_amount` and `expect_token`, that the default token is the network's native USDC, and that the observed amount need only be at least `expect_amount`.

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 — check an x402 receipt proving that a given tx hash paid a given amount to a given address — and the title carries the same specific framing. It is clearly distinguishable from siblings such as x402_payment_status or test_x402_payment without opening any 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?

It gives the operative conditions (token transfers only, native-coin payments yield `no_token_transfer`, amount must be at least `expect_amount`, unsupported networks are 422), which tells an agent when the tool applies. It does not explicitly name sibling alternatives or say when-not to use it versus those, so it stops short of full routing guidance.

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