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

The description goes well beyond the annotations by disclosing the paid nature, exact cost, two-step payment flow, the MCP PaymentRequired response, supported payment parameter locations, and the directive to sign only after budget/policy approval. This is substantial behavioral context that annotations alone do not provide.

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 dense but justified by the payment flow complexity. It front-loads usage and alternatives before payment mechanics. It is longer than ideal, but each section earns its place, and the bracketed payment details are clearly separated from the core usage guidance.

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 the description need not explain return values. The description covers when to use it, when not to, the alternative tool, payment prerequisites, the exact two-step invocation flow, and policy constraints, leaving no critical gap for an agent to call 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 schema already documents both parameters. The description adds value by explaining how _x402_payment is obtained, that it supports a legacy base64 form, and that the modern flow uses params._meta['x402/payment'], which the schema alone does not convey.

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 specific verb and resource: a 'cheapest accumulated reputation lookup' for an agent with a stable agent identifier. It explicitly contrasts with 'Agent Trust Scan' for fresh scans, so an agent can distinguish this tool from its siblings.

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 explicit when-to-use guidance ('Use when an agent already has a stable agent identifier'), a clear alternative with the condition that selects it ('Use Agent Trust Scan instead when there is no usable history or a fresh card scan is required'), and even ordering advice for payment checks ('run free can-pay and readiness checks first').

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