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

Beyond the annotations (readOnly, openWorld, idempotent, non-destructive), it discloses free-tier limits (5 per UTC day) and per-call cost ($0.02 USDC on Base via x402), the required auth mechanism (forward PAYMENT-SIGNATURE), and the exact safety logic behind safe_to_resign (two independent RPC sources agreeing the nonce is unused AND validBefore passed). This is unusually rich behavioral context.

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 front-loaded with the central question and packs inputs, outputs, semantics, and price into a few dense sentences with little waste. The final pricing sentence is long and slightly run-on, but each clause carries necessary information.

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?

There is no output schema, so the description must cover return values — and it does, enumerating the status values (landed|not_landed|pending|canceled|unknown), the retry/resign flags, and the accompanying tx details, terms match, claim pointer, and signed receipt. Inputs, auth, and cost are all covered, leaving nothing essential missing.

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?

With only 50% schema coverage, the description compensates by explaining that payment_payload is the base64 PAYMENT-SIGNATURE previously sent and that from/nonce/(valid_before) form a combined identifying group, adding meaning the schema omits. It still leaves tx_hash, from, and nonce individually undefined.

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 precise scope: checking whether an x402 payment landed and whether it is safe to sign a new one, with the exact input forms accepted. It is clearly a payment-status tool, but it never explicitly contrasts itself with siblings like get_receipt or endpoint_spot_check (the latter appears only in a pricing aside), so it falls short of full sibling differentiation.

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 clear triggering context ("After you pay an x402 endpoint") and spells out the three alternative input modes (payment_payload, tx_hash, or from+nonce+valid_before), which is genuine usage guidance. It does not, however, state when not to reach for this tool versus get_receipt or lookup.

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