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

Beyond the annotations (readOnly=false, destructive=true), the description clarifies that the tool constructs an unsigned transaction, never receives keypair bytes, and that value-moving results must be finalized locally before use. This meaningfully helps an agent avoid assuming on-chain execution happens automatically.

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 core purpose is front-loaded in one sentence, followed by a compact SAP MCP execution guidance block. The guidance is slightly duplicated in the schema description, but the overall text is still concise and scannable.

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 a tool with four parameters, a complete input schema, and an output schema, the description covers intent, pricing, routing, signer boundary, local finalization, and the returned artifact. No critical information needed for invoking it correctly 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?

The input schema already describes all four parameters at 100% coverage, including units for amountUsdc. The description does not add additional per-parameter semantics beyond that, so it appropriately relies on the schema.

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 action and resource: build an unsigned USDC withdraw transaction from a Phoenix trader account and return transactionBase64. This distinguishes it from sibling phoenix builders by operation type, though it does not explicitly contrast or name an alternative.

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 provides explicit operational context: it is a paid hosted builder, estimate cost first, route through sap_payments_call_paid_tool if native x402 is unavailable, and finalize unsigned transactions locally. This is clear guidance for invoking it correctly, but it does not explicitly discuss when to choose this over other phoenix build tools.

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