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

The description discloses several critical behavioral traits beyond annotations: temporary unavailability, paid builder model requiring estimation before building, blocked hosted accountless writes, and the non-custodial signer boundary. These details directly inform safe invocation and are not present in the annotations, which only provide hints on read-only, open-world, idempotency, and destructiveness.

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 front-loaded with the critical unavailability status, followed by structured execution guidance labeled by Intent, Pricing, Routing, and Signer boundary. It is somewhat dense and repeats 'disabled' and 'unavailable,' but each section earns its place and the structure aids parsing.

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?

Given the tool has an output schema (reducing need to explain return values), the description covers essential context: what it does, its current unavailability, pricing, routing constraints, and signer boundary. It lacks a plain declarative 'This tool builds...' but the functionality is implied. Overall, it is quite complete for a disabled builder tool.

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%, with both parameters (owner, domain) fully described in the input schema. The tool description adds no parameter-specific semantics beyond what the schema provides, and the generic instruction to use exact field names is already in the schema description. Therefore, the description does not add value in this dimension.

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 clearly indicates the tool's purpose: setting primary SNS domains, with 'Setting primary SNS domains is disabled' and the title 'Build SNS Set Primary Domain Transaction.' It specifies the resource (SNS primary domain) and the action (build transaction), though it does not explicitly differentiate from sibling SNS build tools beyond the domain-specific focus.

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 strong usage guidance: it is 'Temporarily unavailable' and 'disabled,' telling agents not to use it. It also gives exclusions ('do not call this as a paid hosted write') and an alternative ('Use sap_payments_finalize_transaction when user signing is required'), along with routing and signer boundary context. However, it lacks a direct 'use this tool when...' statement, but the intent is clear from context.

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