Read a customer's billing address

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

With no annotations provided, the description carries the burden, and it explicitly states 'Read-only' as a behavioral guarantee. It also discloses domain significance (address used for invoices, tax identifier driving VAT treatment), which helps the agent anticipate how the result will be used. It does not cover error cases or auth requirements, but for a simple read it is reasonably transparent.

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 compact and front-loaded with the core action, followed by the field list, the read-only caveat, and the practical usage rationale. Every sentence contributes useful information, and there is no repetition or filler.

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 single-parameter read tool with no output schema and no annotations, the description is largely complete: it lists return fields, states the operation is read-only, and explains why the data matters. It could further describe error behavior or absence of a billing address, but the essential agent decision context is present.

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%, so the single required parameter customer_ref is already fully documented. The description adds no additional parameter-level detail, but it does not need to; the baseline of 3 applies when the schema handles parameter semantics completely.

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 uses a specific verb ('Reads') and a concrete resource ('the full billing address of a ProAbono customer'), then enumerates the exact fields returned. It clearly differentiates from siblings like get_customer and update_billing_address by emphasizing the read-only, billing-address-specific scope.

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 context for when to call it: before deciding whether a billing-address update is needed, and notes the billing address is what invoices are issued against. It does not explicitly name alternative tools such as get_customer, but the update-focused usage guidance is clear enough for an agent to select it appropriately.

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