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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: the specific cryptographic/on-chain checks performed, the enumerated authorization states, and the free-vs-paid tiering for self vs third-party receipts.

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 sentences, front-loaded with the core operation and the enumerated checks, followed by the cost model. Dense but nothing is redundant; arguably the state list could have been trimmed, keeping it just shy of ideal.

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?

With an output schema present, return-value explanation is unnecessary, and the rich annotations cover the safety profile. The description completes the picture with checks performed and cost implications; only explicit lifecycle positioning relative to quote/authorize/submit is 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?

Schema description coverage is 100%, so both parameters (payment_intent_id, receipt_id) are already documented in the schema, and the schema correctly labels receipt_id as optional. The description adds no syntax, format, or selection guidance beyond what the schema provides, so the baseline of 3 applies.

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 pairs a specific verb ('Verify') with a precise resource ('IDPHANTOM payment receipt') and then enumerates exactly what verification covers: EIP-712 signature checks, payer recovery, expiry, and on-chain authorization state (free/used/cancelled). That level of detail lets an agent distinguish it from the lifecycle siblings (quote/authorize/submit) even without an explicit comparison.

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 cost-based context ('Free for receipts of payments the caller participated in; paid via the receipt-verifier for third-party receipts'), which helps an agent anticipate charges but is not the same as saying when to call this tool. It never names the sibling tools as alternatives or states preconditions such as 'call after submit_payment'.

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