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

Goes well beyond the annotations: it describes the three outcome values, the verifiable evidence and retry semantics returned, the compliance attestation attached on allow/review, and the origin-binding check on resource_url that can escalate a decision to review. It also discloses that every decision carries an Ed25519-signed receipt verifiable offline against a named public key URL, and warns that a payee/site match is not an endorsement. Annotations only say readOnly/idempotent/openWorld; the description supplies the substantive behavioral contract without contradicting them.

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 essential instruction is front-loaded in the first two sentences, which is good. But the description runs long for a tool with a fully documented schema and output schema, and 'Free, no API key' is repeated at the start and again verbatim at the end, which is pure waste. Some of the middle material (attestation, origin binding) duplicates what the schema and output schema already convey.

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 enumerated, and the description still covers the decision vocabulary, evidence, attestation, receipt verification path, and the escalation logic. Combined with readOnly/idempotent annotations and 100% parameter descriptions, there is nothing an agent needs in order to call this correctly that 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 the schema already explains to, network, resource_url, task, reasoning, amountUsdc and maxAmountUsdc, including the decline-when-over-cap rule and the intent-check opt-in. The description restates 'pass the payee address' and 'pass resource_url (the URL that returned the 402 quote)' but adds no syntax or format detail the schema lacks. Baseline 3 is correct when the schema carries the parameter burden.

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: pass a payee address and get a machine-executable allow|review|decline decision. The core operation is instantly clear and the three-outcome vocabulary is spelled out. It does not, however, distinguish itself from close siblings such as payee_decide, screen_address, or check_payment_request, so an agent cannot tell from this text alone which of these to reach for.

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 a clear trigger ('Call this before every payment your agent makes') and an explicit gating rule: if the decision is not 'allow', do not pay. It even supplies a ready-made test invocation with a known mixer address so the agent can confirm expected behavior. It stops short of naming when NOT to use it or which sibling supersedes it, so there is no exclusion guidance.

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