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

Annotations already indicate readOnlyHint=false and destructiveHint=false. The description usefully adds that this is an unsigned transaction builder, that hosted builders never receive keypair bytes, and that value-moving results must be finalized locally when signing is required. This gives the agent a clear boundary about what the tool will and will not do.

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 tool-specific first sentence is crisp and front-loaded, and the SAP execution guidance is compact despite covering intent, pricing, routing, and signer boundary. The guidance is repeated in the schema description, which is a minor redundancy, but the definition itself is not bloated.

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 two-parameter builder with an output schema, the description is complete: it states what is built, what is returned, how the caller should pay/estimate, how routing should work, and where signing must happen. There is no missing information an agent needs to correctly invoke or carry forward the result.

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 coverage is 100%: authority is described as 'Trader authority public key' and maxPositions as 'Maximum positions (default 8)'. The description adds no parameter-level detail beyond what the schema already provides, so the baseline score of 3 is appropriate.

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 register trader transaction for Phoenix onboarding' and tells the caller the exact return envelope ('Returns transactionBase64'). This clearly distinguishes it from other Phoenix builder siblings like deposit, withdraw, or market-order builders without needing to open their schemas.

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 clear operational context: it is a paid hosted builder, estimate cost first, route through sap_payments_call_paid_tool if needed, and finalize unsigned transactions locally. It does not explicitly contrast this tool with sibling builders, but 'register trader transaction for Phoenix onboarding' and 'unsigned transaction builder' sufficiently establish when it applies.

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