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

Beyond the annotations (readOnly, idempotent, non-destructive), the description adds valuable behavioral detail: whitespace and hyphens are ignored, BSB has no check digit, unknown schemes throw, and ABN validation also flags company status. It fully discloses the tool's limits and edge cases.

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?

Three dense sentences cover the core operation, key edge cases, and limitations without repetition. Important information is front-loaded, and every sentence earns its place.

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?

Despite having no output schema, the description conveys the essential outcome (pass/fail), the ABN company flag, the BSB format-only behavior, and the throw condition. It stops short of specifying the exact return shape, but an agent has enough to invoke the tool 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?

The schema already documents both parameters at 100% coverage, including the enum for type and the note that spaces and hyphens are ignored. The description adds some useful context, such as BSB being format-only, but most parameter meaning is already in 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 verb and resource: 'Validate an Australian ABN, ACN, ARBN, TFN, Medicare or BSB against its official checksum.' It names the exact identifier types and the core operation, making it easy to distinguish from sibling tools like verify_email_address or match_entity_name.

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 context and important exclusions: it is offline and deterministic, and a pass does NOT prove an identifier is issued, active, or held by anyone. This tells the agent when not to rely on the tool, though it does not explicitly name alternative sibling tools.

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