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

Annotations already declare readOnly/openWorld/idempotent/non-destructive, so the safety profile is covered. The description adds two facts annotations cannot convey: the call is paid (0.002 USD) and the payment protocol is x402, which is essential context for an agent deciding whether it can afford to invoke it. It stops short of describing venue coverage or result freshness.

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 fragments, cost first, action second — front-loaded and waste-free. It borders on under-specification rather than verbosity, but every word carries signal.

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?

For an open-world, paid scan with no output schema, the definition leaves meaningful gaps: what venues are compared, what the scan returns (opportunities, spreads, depth?), and how fresh the data is. The payment flow is adequately covered by the schema, but the core value proposition of the scan is only named, not explained.

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?

Only one parameter and schema description coverage is 100%, so the payment_signature semantics (omit to receive payment requirements) are fully documented in the schema. The description adds nothing about the parameter beyond repeating that the call is paid, so baseline 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?

States a specific action and resource: a cross-venue arbitrage scan, plus its paid x402 pricing. An agent can tell it apart from the sibling tools (scorecard, bars, gas, options) since none of them cover arbitrage, though the description never names those alternatives or the venues scanned.

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?

There is no when-to-use guidance, no prerequisites, and no mention of alternatives. The only routing signal is the name itself; the agent must infer that this is the tool for cross-venue arb opportunities rather than, say, mnemos_options_scan.

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